Foot and Ankle Joint Movements Inside Orthoses for Children with Spastic CP Xue-Cheng Liu,1,2 David Embrey,3 Channing Tassone,2 Frederick Klingbeil,4 Carlos Marquez-Barrientos,1 Brenna Brandsma,3 Roger Lyon,1,2 Jeffrey Schwab,2 Sergey Tarima,5 John Thometz2 1
Center for Motion Analysis at Orthopedic Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin 53201, 2Department of Orthopaedic Surgery, Children’s Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee, Wisconsin 53201, 3Children’s Therapy Unit, MulitCare Good Samaritan Hospital, Puyallup, Washington, 4Physical Medicine and Rehabilitation, Children’s Hospital of Wisconsin, Milwaukee, Wisconsin, 5Division of Biostatistics, Medical College of Wisconsin, Milwaukee, Wisconsin Received 10 August 2012; accepted 25 November 2013 Published online 23 December 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jor.22567
ABSTRACT: We compared the ankle joint and foot segment kinematics of pediatric cerebral palsy (CP) participants walking with and without orthoses. A six segment foot model (6SF) was used to track foot motion. Holes were cut in the study orthoses so that electromagnetic markers could be directly placed on the skin. The Hinged Ankle Foot Orthoses (HAFO) allowed a significant increase in ankle dorsiflexion as compared to the barefoot condition during gait, but significantly constrained sagittal forefoot motion and forefoot sagittal range of motion (ROM) (p < 0.01), which may be detrimental. The Solid Ankle Foot Orthoses (SAFO) constrained forefoot ROM as compared to barefoot gait (p < 0.01). The 6SF model did not confirm that the SAFO can control excessive plantarflexion for those with severe plantarflexor spasticity. The supramalleolar orthosis (SMO) significantly (p < 0.01) constrained forefoot ROM as compared to barefoot gait at the beginning and end of the stance phase, which could be detrimental. The SMO had no effects observed in the coronal plane. ß 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:531–536, 2014. Keywords: cerebral palsy; orthoses; gait; foot segment model
Orthoses are a non-surgical option used to assist cerebral palsy (CP) patients with their gait. Patients with CP often walk with equinus, pes valgus, or a combination of the two conditions, and orthoses are assigned to provide a more normal heel strike during the first rocker and more stability during the second rocker, to allow a greater push off moment during the third rocker, and to help prevent excessively plantarflexing feet from catching on the floor during the swing phase.1,2 The effect of different types of orthoses on the gait pattern, step length, cadence, and velocity of children with CP has been studied extensively.3–16 Many studies comparing the different orthoses had the patients use several different types of orthoses in succession.8–14,16 CP patients have a widely varying range of functional ability, so levels of foot deformity and orthoses that might be appropriate for one subject might not be for others.1,17 The supramalleolar orthosis (SMO) may be appropriate for controlling valgus or varus foot deformities, but it will not control plantarflexion or dorsiflexion.2 Solid ankle foot orthoses (SAFO) or hinged ankle foot orthoses (HAFO) might be indicated for excessive plantarflexion during foot loading or the swing phase of the cycle.2 However the HAFO might be inappropriate for children with crouch gait.18 Most studies found that the ankle foot orthoses (AFOs) affect joint kinematics at the ankle joint and have a limited effect on knee kinematics.3,8,9,11 Novacheck et al.18 stated that “consistent and substantial changes in kinematics or kinetics at the pelvis, hip or Grant sponsor: National Institute on Disability and Rehabilitation Research; Grant number: H133G 060155. Correspondence to: Xue-Cheng Liu (T: 414-337-7323; F: 414-337-7337; E-mail: [email protected]) # 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
knee have not been identified” when using AFOs with CP patients. Evidence exists that the shoe, independent of any orthotic worn, can affect gait patterns.19–21 A study on 18 typically developing children found significant differences in the ranges of motion (ROM) of several foot joints between barefoot walking and walking with a shoe.20 The hallux sagittal ROM decreased by 11˚, the tibio-talar sagittal ROM decreased by 4˚, forefoot-hindfoot transverse ROM decreased by 5˚, and the foot progression ROM decreased by 3˚. Another study of 15 hemiplegic children who used orthoses examined differences between barefoot gait, gait with shoes, and gait with an orthotic.21 In that study, shoes significantly affected gait, independent of the orthoses. Many differences between barefoot gait and gait with an orthotic were not present when the comparison was made between gait with shoes and gait with an orthotic. Several studies looking at the influence of orthoses attempted to eliminate the influence of shoes by comparing gait with shoes to gait with orthoses, instead of comparing barefoot gait to gait with orthoses.4,9,15,16,21 In all the studies comparing the effect of orthoses, the markers tracking foot and ankle movement were placed on the outside of the subjects’ shoes or on the orthoses during the walking trials. Studies comparing the effect of different orthoses have not previously measured foot and ankle motion by placing markers directly on anatomical landmarks on the foot surface. We sought to track the kinematics of the ankle joint and foot segments in CP patients, both hemiplegic and diplegic, who use orthoses clinically and to examine kinematic changes with the use of orthoses. Many studies examined the movement of the large lower extremity joints, but we concentrated on tracking JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
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movements of the ankle joint and foot segments.3,6,8,9,11,13 Special orthoses were constructed so that markers could be placed directly on anatomical landmarks to better track foot motion inside the orthoses. All participants used either HAFOs, SAFOs, or SMOs. A six segment foot model (6SF) was used to track ankle joint and foot segment movement.22–24 We hypothesize that: both the HAFO and the SAFO lead to reduced ankle plantarflexion at the first rocker, increased ankle dorsiflexion during the 2nd rocker, and greater ankle dorsiflexion at the 3rd rocker; the SMO affects varus/valgus motion at the midfoot or forefoot; and, for all AFOs, the orthotics reduce dorsiflexion and ROM at the forefoot during the 3rd rocker.
MATERIALS AND METHODS Twenty-three patients with CP participated at two centers: the Children’s Hospital of Wisconsin (Milwaukee, WI) and Good Samaritan Hospital (Puyallup, WA). Ethical approval was obtained from the two Institutional Review Boards prior to performing the study. All participants wore clinically prescribed orthotics and were recruited so that their gait barefoot and with special study orthotics could be compared. Seven participants were hemiplegic, and 16 were diplegic. Depending on their clinically prescribed orthoses, participants were put into an SMO group, a SAFO group, or a HAFO group. Nine participants used SMOs, three used bilateral, and six used unilateral. Five participants used bilateral SAFOs. Ten participants used HAFOs, six bilateral, and four unilateral. One participant wore a right HAFO and a left SMO and was counted both in the HAFO and SMO category. The average age was 8.6 yrs (4.5 to 16.6 yrs). All participants were evaluated by one of two physical therapists and had their function classified using the Gross Motor Function Classification System (GMFCS): 11 participants were level 1, five were level 2, five were level 3, and two were level 4.17 Study orthoses were built for each participant by an experienced pedorthotist. The study orthoses were copies of the participants’ clinically prescribed orthoses. The study orthoses’ soles were modified with slip resistant traction material so that they provided an even contact surface with some traction; this modification allowed participants to walk wearing just the orthoses. Adjustments were made as necessary to ensure that the orthoses fit the participants comfortably; multiple adjustments were sometimes required (Fig. 1). Foot motion during gait was tracked using an Electromagnetic Motion Tracking System (EMTS) composed of StarTrak hardware (Polhemus, VT) and 6D ResearchTM software (Skill Technologies, Phoenix, AZ). The system used square sensors (1.5 cm 1.5 cm) placed on the foot to register movement, and all sensors were attached via a cord to a signal processing box. The marker configuration used was a 6SF model previously used to measure changes in foot motion in normal pediatric subjects.22,23 The external sensors were placed on the foot to track motions of the tibia, calcaneus, cuboid, navicular, 1st metatarsal, and hallux. The markers were placed by palpating anatomic landmarks. The tibia sensor was placed 6 cm below the tibial tuberosity. The calcaneus sensor was placed on the heel 1.5 cm above the bottom of the foot pad. The navicular sensor was placed on the navicular tuberosity. The cuboid sensor was placed on the cuboid indentation. The 1st metatarsal sensor was placed JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
Figure 1. A set-up of the 6FS model measurements with and without orthoses: (A) 6 sensors placed on the anatomical landmarks. (B) Sensors placed on the anatomical landmarks through the windows on the orthoses.
in the center of the 1st metatarsal; the center was found by palpating and outlining the border of the bone, and measuring the center using the outline. The hallux sensor was placed in the center of the hallux. All placements were done by one of two trained investigators. Elastic bandages were wrapped around the sensor’s cords to prevent the markers being pulled by the cords. To allow marker placement on the anatomic landmarks of the foot, holes were cut in the orthoses by a pedorthotist. When switching from the barefoot trials to the orthotic trials, the foot sensors (usually the calcaneus, cuboid, and navicular) often had to be removed and replaced on the foot. If possible, sensors were not repositioned between trials. Participants walked at a selfselected pace in the barefoot and orthotic trials. At least two data sets were gathered for both barefoot and the orthotic trials. A few participants required parental assistance or used assistive devices during the trials. Four participants used a walker or cane during the assessment, and three required parental support.
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Figure 2. The positioning device used to help ensure a consistent posture between the barefoot standing trials and the trials using the AFOs. An outline of the feet was also used to ensure a consistent foot position between barefoot and AFO trials.
Before the barefoot data were gathered, participants stood in their neutral standing position and the marker coordinates on the foot were set to zero, so that all rotation measurements gathered were with respect to the participants’ neutral standing position. In this position, all markers had the sagittal plane defined as being in the AP direction, the transverse plane as parallel to the floor, and the coronal plane perpendicular to the floor, such that hindfoot inversion/eversion was in the coronal plane. During motion, the plane orientations moved with the foot. All movement was measured as the rotation between the markers on the different anatomical landmarks for each joint. A custom built positioning device, made of PVC piping, in conjunction with a foot tracing, was used to measure the barefoot neutral standing postures (Fig. 2). If a sensor fell off during testing, the participant was repositioned to the neutral standing position using the barefoot foot tracing and positioning device, and the marker measurements were reset to zero. Before the orthotic data were gathered, participants were positioned in an approximation of the barefoot neutral position using the PVC position device and the foot tracing
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made during the barefoot neutral standing position. While standing in the approximate barefoot neutral standing position, the markers’ coordinates were set to zero so that all measurements gathered were with respect to the neutral standing position with the orthotics, which was different than the barefoot neutral standing position. The movements of the following foot segments were tracked: tibia-calcaneus (ankle), calcaneus-cuboid (calc-cub), navicular-1st metatarsal (midfoot), and 1st metatarsal-hallux (forefoot). For all joints, motion in the sagittal plane was defined as dorsiflexion/plantarflexion, motion in the coronal plane as inversion/eversion, and motion in the transverse plane as external/internal rotation. Kinematic data were divided into stance and swing phases by examining the recorded motion. The stance phase was then sub-divided into four intervals25: Loading Response (LR: 0–17% stance), MidStance (MSt: 17–50% stance), Terminal Stance (TSt: 50–83% stance), and Pre-Swing (PSw: 83–100% stance). The swing phase was sub-divided into three intervals25: Initial Swing (ISw: 0–33% swing), Mid-Swing (MSw: 33–68% swing), and Terminal Swing (TSw: 68–100% swing). A custom Matlab program was built to calculate the mean angle of rotation and ROM for each joint during each subdivision of the gait cycle. All changes 5˚ only 3.5% of the time.27 For the ankle and forefoot, a reliability study of the 6SF model showed moderate to high inter-rater and intra-rater reliability in the sagittal and coronal planes (ICC 0.36 to 0.94) and low reliability in the transverse plane (ICC < 0.30).24 A Wilcoxon ranked sign test for paired comparisons was used to determine significant differences between the kinematic data gathered for the barefoot and orthotic trials. Nonparametric tests were used because of the presence of skewed distributions. The participants were grouped according to the type of orthotic worn: HAFO, SMO, and SAFO. The Wilcoxon test was run on seven sub-divisions of the gait cycle (four intervals during stance, three intervals during swing). A p-value < 0.01 was considered significant to compensate for multiple comparisons.
Table 1. Significant Differences Between Barefoot and HAFO Walking for the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) HAFO Variable Mean Value
ROM
Joint
Plane
Ankle
S
Forefoot
S
Forefoot
S
Phase LR TSt PSw ISw PSw ISw TSw TSt ISw
Barefoot
HAFO
p Value
0.4 5.3 2.1 6.1 0.5 8.1 2.7 9.2 19.0 11.1 12.9 10.3 12.2 8.2 11.3 5.5 7.7 4.7
4.8 6.8 7.7 7.6 6.6 9.7 5.2 8.8 6.1 3.4 3.8 4.2 5.2 4.1 4.8 2.2 2.4 1.7
0.001 0.003 0.001 0.001 0.001 0.004 0.007 0.0001 0.0001
Note. S, Sagittal; C, Coronal; T, Transverse. In the sagittal plane; aþ value denotes dorsiflexion. In the coronal plane, aþ value denotes inversion. In the transverse plane, aþ value denotes internal rotation. JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
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RESULTS The HAFO caused significant kinematic differences to emerge at the ankle and forefoot in the sagittal plane (Table 1). No significant mean value changes were observed using the HAFO at the calc-cub or midfoot. At the ankle joint, the HAFO increased mean dorsiflexion significantly through much of the gait cycle, with the increase ranging from 5.2˚ to 7.9˚ (p < 0.003). At the forefoot the HAFO decreased mean dorsiflexion at the end of the stance phase and through much of swing, with the decrease ranging from 7˚ to 12.9˚ (p < 0.004) (Fig. 3). The HAFO decreased ROM at the forefoot at TSt by 6.4˚ and at the first part of swing by 5.2˚ (p < 0.007). No significant ROM changes were observed using the HAFO at the ankle, calc-cub, or midfoot.
No significant mean value changes were observed using the SAFO >5˚ at any joint. The SAFO caused a significant decrease of 5.2˚ in forefoot sagittal ROM during TSt (p < 0.004) (Table 2). No significant ROM changes were observed using the SAFO at the ankle, calc-cub, or midfoot. The SMO caused significant kinematic differences at the mid-foot and forefoot (Table 3). No significant mean value changes were observed using the SMO at the ankle or calc-cub. At the midfoot joint, the SMO increased mean dorsiflexion at ISw by 5.3˚ (p < 0.002). At the forefoot joint the SMO decreased mean dorsiflexion at PSw and the swing phase, with dorsiflexion decreasing from 11.0˚ to 13.5˚ (p < 0.003). At the forefoot joint, the SMO decreased the sagittal ROM at LR by 5.9˚ and at TSt by 7.1˚ (p < 0.001). No significant ROM changes were observed using the SMO at the ankle, calc-cub, or midfoot greater.
DISCUSSION
Figure 3. Comparison of forefoot dorsiflexion and plantarflexion, with and without orthoses, for the (A) HAFO (B) SAFO and (C) SMO groups. JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
The use of the HAFO decreased plantarflexion at the ankle joint during the 1st rocker and increased dorsiflexion at the 3rd rocker as hypothesized. Increased dorsiflexion at the ankle joint allows for increased stability during initial contact and can allow greater push off moment generation during terminal stance.4,10 However, no effect was seen during the 2nd rocker at the ankle joint, where a reduction in plantarflexion was expected for a spastic CP patient. As hypothesized, at the forefoot there was a decrease in dorsiflexion and in the sagittal ROM at the 3rd rocker. This loss of mobility could be detrimental since during the 3rd rocker forefoot dorsiflexion is necessary for force generation at toe off.25 While the effect of the HAFO on ankle dorsiflexion was previously documented, the effect at the forefoot joint was not. The SAFO decreased the forefoot ROM as hypothesized during the 3rd rocker, which was probably detrimental for force generation during toe off, but no other effects expected were detected.25 Our results are consistent with previous studies that showed that the HAFO allows more normal dorsiflexion compared to the SAFO during the 3rd rocker,4,15 although concern exists that the HAFO can allow too much dorsiflexion and encourage crouch gait.8 Changes in ankle dorsiflexion were not observed, although the SAFO is meant to control excessive ankle plantarflexion during the 1st rocker and the swing phase.2 While the SAFO does not change the foot’s dorsiflexion, it may provide a better contact surface during the 1st rocker. The SAFO is often used in the most severe cases for patients who have less muscle control and strength and need more stability.18,28 Unexpectedly, the SMO increased dorsiflexion at the midfoot during the first part of swing, which has not been noted previously with the single segment foot models. This result agrees with statements that SMOs may influence sagittal motion during the swing phase,18 although it contrasts to previous results that
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Table 2. Significant Differences Between Barefoot and SAFO walking For the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) SAFO Variable ROM
Joint
Plane
Phase
Barefoot
SAFO
p Value
Forefoot
S
TSt
10.7 5.7
5.1 2.9
0.004
the SMO does not influence sagittal plane motion.9,16 No effect was seen in the coronal plane at any joint, which may indicate that the SMO does not affect coronal motion. As hypothesized, the SMO decreased dorsiflexion at the forefoot at the end of the 3rd rocker and decreased the forefoot sagittal ROM during the 3rd rocker. An unexpected decrease in dorsiflexion occurred at forefoot during swing, and a decrease in forefoot sagittal ROM was also seen during the 1st rocker. Similar to the HAFO and SAFO, the SMO apparently causes a loss of mobility at the forefoot joint that may interfere with the foot’s ability to transfer the body’s weight to the forefoot during TSt. Several factors make this study unique. Most other investigators only attached surface markers to shoes during walking trials but did not track the movement of the underlying foot segments. Also most other investigators used a single segment foot model and only examined the effect of orthoses at the ankle, instead of the effects at the various foot segments. In contrast to many other studies in which subjects wore a succession of different orthotic types, in our study participants used orthoses that matched their clinically prescribed orthoses. The type of orthotic that may be beneficial to a CP patient, if one would be beneficial at all, is highly dependent on an individual’s gait patterns and functional deficiencies.28 Our study has several limitations. Use of the study orthotics altered the subjects’ normal gait to an unknown degree. The biomechanics of the orthoses were modified since small holes were cut to allow marker placement on the foot, which may have compromised the orthotic’s stiffness. The feel of wearing the study orthotics without shoes may be different
for the subjects than wearing their clinically prescribed orthotics with shoes, which may have altered the subjects gait to an unknown degree. Some patients may have been prescribed orthotics that were not suited to their needs, which means that observed lacks of improvement may be due to improper orthotic prescription. The 6SF model could only measure changes in foot segment orientation between the barefoot condition and the AFO condition; for other studies looking at foot deformity, other models may be more appropriate. The neutral standing positions for the barefoot and orthotic trials were probably slightly different, and since the neutral positions were the baseline reference points for all kinematic measurements, the measurements for the two conditions may be different. In the future, the neutral standing position differences might be corrected by using offsets measured by X-ray or CT scan. We did not examine the kinematics of the knee, hip, and pelvis, but a consistent effect on the kinematics of the those joints has not been identified with the use of orthoses and merits further study.18 The HAFO is considered effective in controlling excessive plantarflexion while not constraining dorsiflexion, but the 6SF model shows that it may detrimentally constrain forefoot motion. The 6SF model used cannot confirm that the SAFO can control excessive plantarflexion, but the SAFO may still play an important part in increasing gait stability and balance.7 The SMO showed no evidence that it controlled foot inversion at the midfoot joint, and evidence is lacking that the SMO corrects hindfoot or forefoot inversion. The SMO also showed evidence that, like the HAFO and SAFO, it could detrimentally constrain forefoot motion.
Table 3. Significant Differences Between Barefoot and SMO Walking for the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) SMO Joint
Plane
Phase
Barefoot
SMO
p Value
Mean Value
Midfoot Forefoot
S S
ROM
Forefoot
S
ISw PSw ISw MSw TSw LR TSt
8.2 6.2 21.6 6.7 14.2 6.5 10.2 6.4 14.7 4.7 9.6 4.5 15.3 4.4
2.9 5.0 8.1 7.4 2.1 7.4 0.8 8.1 2.6 7.1 3.6 2.6 8.2 2.5
0.002 0.002 0.001 0.001 0.003 0.001 0.001
Variable
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REFERENCES 1. Davids JR. 2010. The foot and ankle in cerebral palsy. Orthop Clin North Am 41:579–593. 2. Davids JR, Rowan F, Davis RB. 2007. Indications for orthoses to improve gait in children with cerebral palsy. J Am Acad Orthop Surg 15:178–188. 3. Abel MF, Juhl GA, Vaughan CL, et al. 1998. Gait assessment of fixed ankle-foot orthoses in children with spastic diplegia. Arch Phys Med Rehabil 79:126–133. 4. Rethlefsen S, Kay R, Dennis S, et al. 1999. The effects of fixed and articulated ankle-foot orthoses on gait patterns in subjects with cerebral palsy. J Pediatr Orthop 19:470–474. 5. White H, Jenkins J, Neace WP, et al. 2002. Clinically prescribed orthoses demonstrate an increase in velocity of gait in children with cerebral palsy: a retrospective study. Dev Med Child Neurol 44:227–232. 6. Hayek S, Hemo Y, Chamis S, et al. 2007. The effect of community-prescribed ankle-foot orthoses on gait parameters in children with spastic cerebral palsy. J Child Orthop 1:325–332. 7. Figueiredo EM, Ferreira GB, Maia Moreira RC, et al. 2008. Efficacy of ankle-foot orthoses on gait of children with cerebral palsy: systematic review of literature. Pediatr Phys Ther 20:207–223. 8. Buckon CE, Thomas SS, Jakobson-Huston S, et al. 2004. Comparison of three ankle-foot orthosis configurations for children with spastic diplegia. Dev Med Child Neurol 46:590–598. 9. Carlson WE, Vaughan CL, Damiano DL, et al. 1997. Orthotic management of gait in spastic diplegia. Am J Phys Med Rehabil 76:219–225. 10. Radtka SA, Skinner SR, Johanson ME. 2005. A comparison of gait with solid and hinged ankle-foot orthoses in children with spastic diplegic cerebral palsy. Gait Posture 21:303– 310. 11. Buckon CE, Thomas SS, Jakobson-Huston S, et al. 2001. Comparison of three ankle-foot orthosis configurations for children with spastic hemiplegia. Dev Med Child Neurol 43:371–378. 12. Lam WK, Leong JC, Li YH, et al. 2005. Biomechanical and electromyographic evaluation of ankle foot orthosis and dynamic ankle foot orthosis in spastic cerebral palsy. Gait Posture 22:189–197. 13. Radtka SA, Skinner SR, Dixon DM, et al. 1997. A comparison of gait with solid, dynamic, and no ankle-foot orthoses in children with spastic cerebral palsy. Phys Ther 77:395–409. 14. Romkes J, Brunner R. 2002. Comparison of a dynamic and a hinged ankle-foot orthosis by gait analysis in patients with hemiplegic cerebral palsy. Gait Posture 15:18–24. 15. Smiley SJ, Jacobsen FS, Mielke C, et al. 2002. A comparison of the effects of solid, articulated, and posterior leaf-spring
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ankle-foot orthoses and shoes alone on gait and energy expenditure in children with spastic diplegic cerebral palsy. Orthopedics 25:411–415. Crenshaw S, Herzog R, Castagno P, et al. 2000. The efficacy of tone-reducing features in orthotics on the gait of children with spastic diplegic cerebral palsy. J Pediatr Orthop 20:210–216. Palisano R, Rosenbaum P, Walter S, et al. 1997. Development and reliability of a system to classify gross motor function in children with cerebral palsy. Dev Med Child Neurol 39:214–223. Novacheck TF, Kroll GJ, Gent G, et al. 2009. Orthoses. In: Gage J, Schwartz M, Koop S, Novacheck TF, editors. The Identification and treatment of gait problems in cerebral palsy, 2nd ed. London: Mac Keith Press. p 327–348. Hesse S, Luecke D, Jahnke MT, et al. 1996. Gait function in spastic hemiparetic patients walking barefoot, with firm shoes, and with ankle-foot orthosis. Int J Rehabil Res 19:133–141. Wolf S, Simon J, Patikas D, et al. 2008. Foot motion in children shoes: a comparison of barefoot walking with shod walking in conventional and flexible shoes. Gait Posture 27:51–59. Desloovere K, Molenaers G, Van Gestel L, et al. 2006. How can push-off be preserved during use of an ankle foot orthosis in children with hemiplegia? A prospective controlled study Gait Posture 24:142–151. Marquez-Barrientos C, Liu XC, Thometz J, et al. Comparison of Six-Segment-Foot Movements between MRI and Motion System in TD Children. GCMAS, May 12-15, 2010; Miami, FL. Liu XC, Thometz J, Lyon R, et al. Six-segmental foot model using ETS 20th ISB/29th ASB; 07/31-08/05, 2005; Cleveland, OH. Liu XC, Embrey D, Lyon R, et al. Does the anatomical foot and ankle motion really change following orthotic intervention in children with spastic CP? Gait and Clinical Movement Analysis Society; May 12–15, 2010; Miami, FL. Perry J, Burnfield J. 1992. Gait analysis: normal and pathological function, 1st ed. Thorofare: Slack Incorporated. Kobayashi K, Gransberg L, Knutsson E, et al. 1997. A new system for three-dimensional gait recording using electromagnetic tracking. Gait Posture 6:63–75. Nester C, Jones RK, Liu A, et al. 2007. Foot kinematics during walking measured using bone and surface mounted markers. J Biomech 40:3412–3423. Molnar GE. 1995. Orthotic management of children. In: Redford JB, editor. Orthotics: clinical practice and rehabilitiation, technology, 1 ed. Philadelphia: Churchill Livingstone. p 137–165.
Center for Motion Analysis at Orthopedic Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin 53201, 2Department of Orthopaedic Surgery, Children’s Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee, Wisconsin 53201, 3Children’s Therapy Unit, MulitCare Good Samaritan Hospital, Puyallup, Washington, 4Physical Medicine and Rehabilitation, Children’s Hospital of Wisconsin, Milwaukee, Wisconsin, 5Division of Biostatistics, Medical College of Wisconsin, Milwaukee, Wisconsin Received 10 August 2012; accepted 25 November 2013 Published online 23 December 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jor.22567
ABSTRACT: We compared the ankle joint and foot segment kinematics of pediatric cerebral palsy (CP) participants walking with and without orthoses. A six segment foot model (6SF) was used to track foot motion. Holes were cut in the study orthoses so that electromagnetic markers could be directly placed on the skin. The Hinged Ankle Foot Orthoses (HAFO) allowed a significant increase in ankle dorsiflexion as compared to the barefoot condition during gait, but significantly constrained sagittal forefoot motion and forefoot sagittal range of motion (ROM) (p < 0.01), which may be detrimental. The Solid Ankle Foot Orthoses (SAFO) constrained forefoot ROM as compared to barefoot gait (p < 0.01). The 6SF model did not confirm that the SAFO can control excessive plantarflexion for those with severe plantarflexor spasticity. The supramalleolar orthosis (SMO) significantly (p < 0.01) constrained forefoot ROM as compared to barefoot gait at the beginning and end of the stance phase, which could be detrimental. The SMO had no effects observed in the coronal plane. ß 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:531–536, 2014. Keywords: cerebral palsy; orthoses; gait; foot segment model
Orthoses are a non-surgical option used to assist cerebral palsy (CP) patients with their gait. Patients with CP often walk with equinus, pes valgus, or a combination of the two conditions, and orthoses are assigned to provide a more normal heel strike during the first rocker and more stability during the second rocker, to allow a greater push off moment during the third rocker, and to help prevent excessively plantarflexing feet from catching on the floor during the swing phase.1,2 The effect of different types of orthoses on the gait pattern, step length, cadence, and velocity of children with CP has been studied extensively.3–16 Many studies comparing the different orthoses had the patients use several different types of orthoses in succession.8–14,16 CP patients have a widely varying range of functional ability, so levels of foot deformity and orthoses that might be appropriate for one subject might not be for others.1,17 The supramalleolar orthosis (SMO) may be appropriate for controlling valgus or varus foot deformities, but it will not control plantarflexion or dorsiflexion.2 Solid ankle foot orthoses (SAFO) or hinged ankle foot orthoses (HAFO) might be indicated for excessive plantarflexion during foot loading or the swing phase of the cycle.2 However the HAFO might be inappropriate for children with crouch gait.18 Most studies found that the ankle foot orthoses (AFOs) affect joint kinematics at the ankle joint and have a limited effect on knee kinematics.3,8,9,11 Novacheck et al.18 stated that “consistent and substantial changes in kinematics or kinetics at the pelvis, hip or Grant sponsor: National Institute on Disability and Rehabilitation Research; Grant number: H133G 060155. Correspondence to: Xue-Cheng Liu (T: 414-337-7323; F: 414-337-7337; E-mail: [email protected]) # 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
knee have not been identified” when using AFOs with CP patients. Evidence exists that the shoe, independent of any orthotic worn, can affect gait patterns.19–21 A study on 18 typically developing children found significant differences in the ranges of motion (ROM) of several foot joints between barefoot walking and walking with a shoe.20 The hallux sagittal ROM decreased by 11˚, the tibio-talar sagittal ROM decreased by 4˚, forefoot-hindfoot transverse ROM decreased by 5˚, and the foot progression ROM decreased by 3˚. Another study of 15 hemiplegic children who used orthoses examined differences between barefoot gait, gait with shoes, and gait with an orthotic.21 In that study, shoes significantly affected gait, independent of the orthoses. Many differences between barefoot gait and gait with an orthotic were not present when the comparison was made between gait with shoes and gait with an orthotic. Several studies looking at the influence of orthoses attempted to eliminate the influence of shoes by comparing gait with shoes to gait with orthoses, instead of comparing barefoot gait to gait with orthoses.4,9,15,16,21 In all the studies comparing the effect of orthoses, the markers tracking foot and ankle movement were placed on the outside of the subjects’ shoes or on the orthoses during the walking trials. Studies comparing the effect of different orthoses have not previously measured foot and ankle motion by placing markers directly on anatomical landmarks on the foot surface. We sought to track the kinematics of the ankle joint and foot segments in CP patients, both hemiplegic and diplegic, who use orthoses clinically and to examine kinematic changes with the use of orthoses. Many studies examined the movement of the large lower extremity joints, but we concentrated on tracking JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
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movements of the ankle joint and foot segments.3,6,8,9,11,13 Special orthoses were constructed so that markers could be placed directly on anatomical landmarks to better track foot motion inside the orthoses. All participants used either HAFOs, SAFOs, or SMOs. A six segment foot model (6SF) was used to track ankle joint and foot segment movement.22–24 We hypothesize that: both the HAFO and the SAFO lead to reduced ankle plantarflexion at the first rocker, increased ankle dorsiflexion during the 2nd rocker, and greater ankle dorsiflexion at the 3rd rocker; the SMO affects varus/valgus motion at the midfoot or forefoot; and, for all AFOs, the orthotics reduce dorsiflexion and ROM at the forefoot during the 3rd rocker.
MATERIALS AND METHODS Twenty-three patients with CP participated at two centers: the Children’s Hospital of Wisconsin (Milwaukee, WI) and Good Samaritan Hospital (Puyallup, WA). Ethical approval was obtained from the two Institutional Review Boards prior to performing the study. All participants wore clinically prescribed orthotics and were recruited so that their gait barefoot and with special study orthotics could be compared. Seven participants were hemiplegic, and 16 were diplegic. Depending on their clinically prescribed orthoses, participants were put into an SMO group, a SAFO group, or a HAFO group. Nine participants used SMOs, three used bilateral, and six used unilateral. Five participants used bilateral SAFOs. Ten participants used HAFOs, six bilateral, and four unilateral. One participant wore a right HAFO and a left SMO and was counted both in the HAFO and SMO category. The average age was 8.6 yrs (4.5 to 16.6 yrs). All participants were evaluated by one of two physical therapists and had their function classified using the Gross Motor Function Classification System (GMFCS): 11 participants were level 1, five were level 2, five were level 3, and two were level 4.17 Study orthoses were built for each participant by an experienced pedorthotist. The study orthoses were copies of the participants’ clinically prescribed orthoses. The study orthoses’ soles were modified with slip resistant traction material so that they provided an even contact surface with some traction; this modification allowed participants to walk wearing just the orthoses. Adjustments were made as necessary to ensure that the orthoses fit the participants comfortably; multiple adjustments were sometimes required (Fig. 1). Foot motion during gait was tracked using an Electromagnetic Motion Tracking System (EMTS) composed of StarTrak hardware (Polhemus, VT) and 6D ResearchTM software (Skill Technologies, Phoenix, AZ). The system used square sensors (1.5 cm 1.5 cm) placed on the foot to register movement, and all sensors were attached via a cord to a signal processing box. The marker configuration used was a 6SF model previously used to measure changes in foot motion in normal pediatric subjects.22,23 The external sensors were placed on the foot to track motions of the tibia, calcaneus, cuboid, navicular, 1st metatarsal, and hallux. The markers were placed by palpating anatomic landmarks. The tibia sensor was placed 6 cm below the tibial tuberosity. The calcaneus sensor was placed on the heel 1.5 cm above the bottom of the foot pad. The navicular sensor was placed on the navicular tuberosity. The cuboid sensor was placed on the cuboid indentation. The 1st metatarsal sensor was placed JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
Figure 1. A set-up of the 6FS model measurements with and without orthoses: (A) 6 sensors placed on the anatomical landmarks. (B) Sensors placed on the anatomical landmarks through the windows on the orthoses.
in the center of the 1st metatarsal; the center was found by palpating and outlining the border of the bone, and measuring the center using the outline. The hallux sensor was placed in the center of the hallux. All placements were done by one of two trained investigators. Elastic bandages were wrapped around the sensor’s cords to prevent the markers being pulled by the cords. To allow marker placement on the anatomic landmarks of the foot, holes were cut in the orthoses by a pedorthotist. When switching from the barefoot trials to the orthotic trials, the foot sensors (usually the calcaneus, cuboid, and navicular) often had to be removed and replaced on the foot. If possible, sensors were not repositioned between trials. Participants walked at a selfselected pace in the barefoot and orthotic trials. At least two data sets were gathered for both barefoot and the orthotic trials. A few participants required parental assistance or used assistive devices during the trials. Four participants used a walker or cane during the assessment, and three required parental support.
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Figure 2. The positioning device used to help ensure a consistent posture between the barefoot standing trials and the trials using the AFOs. An outline of the feet was also used to ensure a consistent foot position between barefoot and AFO trials.
Before the barefoot data were gathered, participants stood in their neutral standing position and the marker coordinates on the foot were set to zero, so that all rotation measurements gathered were with respect to the participants’ neutral standing position. In this position, all markers had the sagittal plane defined as being in the AP direction, the transverse plane as parallel to the floor, and the coronal plane perpendicular to the floor, such that hindfoot inversion/eversion was in the coronal plane. During motion, the plane orientations moved with the foot. All movement was measured as the rotation between the markers on the different anatomical landmarks for each joint. A custom built positioning device, made of PVC piping, in conjunction with a foot tracing, was used to measure the barefoot neutral standing postures (Fig. 2). If a sensor fell off during testing, the participant was repositioned to the neutral standing position using the barefoot foot tracing and positioning device, and the marker measurements were reset to zero. Before the orthotic data were gathered, participants were positioned in an approximation of the barefoot neutral position using the PVC position device and the foot tracing
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made during the barefoot neutral standing position. While standing in the approximate barefoot neutral standing position, the markers’ coordinates were set to zero so that all measurements gathered were with respect to the neutral standing position with the orthotics, which was different than the barefoot neutral standing position. The movements of the following foot segments were tracked: tibia-calcaneus (ankle), calcaneus-cuboid (calc-cub), navicular-1st metatarsal (midfoot), and 1st metatarsal-hallux (forefoot). For all joints, motion in the sagittal plane was defined as dorsiflexion/plantarflexion, motion in the coronal plane as inversion/eversion, and motion in the transverse plane as external/internal rotation. Kinematic data were divided into stance and swing phases by examining the recorded motion. The stance phase was then sub-divided into four intervals25: Loading Response (LR: 0–17% stance), MidStance (MSt: 17–50% stance), Terminal Stance (TSt: 50–83% stance), and Pre-Swing (PSw: 83–100% stance). The swing phase was sub-divided into three intervals25: Initial Swing (ISw: 0–33% swing), Mid-Swing (MSw: 33–68% swing), and Terminal Swing (TSw: 68–100% swing). A custom Matlab program was built to calculate the mean angle of rotation and ROM for each joint during each subdivision of the gait cycle. All changes 5˚ only 3.5% of the time.27 For the ankle and forefoot, a reliability study of the 6SF model showed moderate to high inter-rater and intra-rater reliability in the sagittal and coronal planes (ICC 0.36 to 0.94) and low reliability in the transverse plane (ICC < 0.30).24 A Wilcoxon ranked sign test for paired comparisons was used to determine significant differences between the kinematic data gathered for the barefoot and orthotic trials. Nonparametric tests were used because of the presence of skewed distributions. The participants were grouped according to the type of orthotic worn: HAFO, SMO, and SAFO. The Wilcoxon test was run on seven sub-divisions of the gait cycle (four intervals during stance, three intervals during swing). A p-value < 0.01 was considered significant to compensate for multiple comparisons.
Table 1. Significant Differences Between Barefoot and HAFO Walking for the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) HAFO Variable Mean Value
ROM
Joint
Plane
Ankle
S
Forefoot
S
Forefoot
S
Phase LR TSt PSw ISw PSw ISw TSw TSt ISw
Barefoot
HAFO
p Value
0.4 5.3 2.1 6.1 0.5 8.1 2.7 9.2 19.0 11.1 12.9 10.3 12.2 8.2 11.3 5.5 7.7 4.7
4.8 6.8 7.7 7.6 6.6 9.7 5.2 8.8 6.1 3.4 3.8 4.2 5.2 4.1 4.8 2.2 2.4 1.7
0.001 0.003 0.001 0.001 0.001 0.004 0.007 0.0001 0.0001
Note. S, Sagittal; C, Coronal; T, Transverse. In the sagittal plane; aþ value denotes dorsiflexion. In the coronal plane, aþ value denotes inversion. In the transverse plane, aþ value denotes internal rotation. JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
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RESULTS The HAFO caused significant kinematic differences to emerge at the ankle and forefoot in the sagittal plane (Table 1). No significant mean value changes were observed using the HAFO at the calc-cub or midfoot. At the ankle joint, the HAFO increased mean dorsiflexion significantly through much of the gait cycle, with the increase ranging from 5.2˚ to 7.9˚ (p < 0.003). At the forefoot the HAFO decreased mean dorsiflexion at the end of the stance phase and through much of swing, with the decrease ranging from 7˚ to 12.9˚ (p < 0.004) (Fig. 3). The HAFO decreased ROM at the forefoot at TSt by 6.4˚ and at the first part of swing by 5.2˚ (p < 0.007). No significant ROM changes were observed using the HAFO at the ankle, calc-cub, or midfoot.
No significant mean value changes were observed using the SAFO >5˚ at any joint. The SAFO caused a significant decrease of 5.2˚ in forefoot sagittal ROM during TSt (p < 0.004) (Table 2). No significant ROM changes were observed using the SAFO at the ankle, calc-cub, or midfoot. The SMO caused significant kinematic differences at the mid-foot and forefoot (Table 3). No significant mean value changes were observed using the SMO at the ankle or calc-cub. At the midfoot joint, the SMO increased mean dorsiflexion at ISw by 5.3˚ (p < 0.002). At the forefoot joint the SMO decreased mean dorsiflexion at PSw and the swing phase, with dorsiflexion decreasing from 11.0˚ to 13.5˚ (p < 0.003). At the forefoot joint, the SMO decreased the sagittal ROM at LR by 5.9˚ and at TSt by 7.1˚ (p < 0.001). No significant ROM changes were observed using the SMO at the ankle, calc-cub, or midfoot greater.
DISCUSSION
Figure 3. Comparison of forefoot dorsiflexion and plantarflexion, with and without orthoses, for the (A) HAFO (B) SAFO and (C) SMO groups. JOURNAL OF ORTHOPAEDIC RESEARCH APRIL 2014
The use of the HAFO decreased plantarflexion at the ankle joint during the 1st rocker and increased dorsiflexion at the 3rd rocker as hypothesized. Increased dorsiflexion at the ankle joint allows for increased stability during initial contact and can allow greater push off moment generation during terminal stance.4,10 However, no effect was seen during the 2nd rocker at the ankle joint, where a reduction in plantarflexion was expected for a spastic CP patient. As hypothesized, at the forefoot there was a decrease in dorsiflexion and in the sagittal ROM at the 3rd rocker. This loss of mobility could be detrimental since during the 3rd rocker forefoot dorsiflexion is necessary for force generation at toe off.25 While the effect of the HAFO on ankle dorsiflexion was previously documented, the effect at the forefoot joint was not. The SAFO decreased the forefoot ROM as hypothesized during the 3rd rocker, which was probably detrimental for force generation during toe off, but no other effects expected were detected.25 Our results are consistent with previous studies that showed that the HAFO allows more normal dorsiflexion compared to the SAFO during the 3rd rocker,4,15 although concern exists that the HAFO can allow too much dorsiflexion and encourage crouch gait.8 Changes in ankle dorsiflexion were not observed, although the SAFO is meant to control excessive ankle plantarflexion during the 1st rocker and the swing phase.2 While the SAFO does not change the foot’s dorsiflexion, it may provide a better contact surface during the 1st rocker. The SAFO is often used in the most severe cases for patients who have less muscle control and strength and need more stability.18,28 Unexpectedly, the SMO increased dorsiflexion at the midfoot during the first part of swing, which has not been noted previously with the single segment foot models. This result agrees with statements that SMOs may influence sagittal motion during the swing phase,18 although it contrasts to previous results that
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Table 2. Significant Differences Between Barefoot and SAFO walking For the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) SAFO Variable ROM
Joint
Plane
Phase
Barefoot
SAFO
p Value
Forefoot
S
TSt
10.7 5.7
5.1 2.9
0.004
the SMO does not influence sagittal plane motion.9,16 No effect was seen in the coronal plane at any joint, which may indicate that the SMO does not affect coronal motion. As hypothesized, the SMO decreased dorsiflexion at the forefoot at the end of the 3rd rocker and decreased the forefoot sagittal ROM during the 3rd rocker. An unexpected decrease in dorsiflexion occurred at forefoot during swing, and a decrease in forefoot sagittal ROM was also seen during the 1st rocker. Similar to the HAFO and SAFO, the SMO apparently causes a loss of mobility at the forefoot joint that may interfere with the foot’s ability to transfer the body’s weight to the forefoot during TSt. Several factors make this study unique. Most other investigators only attached surface markers to shoes during walking trials but did not track the movement of the underlying foot segments. Also most other investigators used a single segment foot model and only examined the effect of orthoses at the ankle, instead of the effects at the various foot segments. In contrast to many other studies in which subjects wore a succession of different orthotic types, in our study participants used orthoses that matched their clinically prescribed orthoses. The type of orthotic that may be beneficial to a CP patient, if one would be beneficial at all, is highly dependent on an individual’s gait patterns and functional deficiencies.28 Our study has several limitations. Use of the study orthotics altered the subjects’ normal gait to an unknown degree. The biomechanics of the orthoses were modified since small holes were cut to allow marker placement on the foot, which may have compromised the orthotic’s stiffness. The feel of wearing the study orthotics without shoes may be different
for the subjects than wearing their clinically prescribed orthotics with shoes, which may have altered the subjects gait to an unknown degree. Some patients may have been prescribed orthotics that were not suited to their needs, which means that observed lacks of improvement may be due to improper orthotic prescription. The 6SF model could only measure changes in foot segment orientation between the barefoot condition and the AFO condition; for other studies looking at foot deformity, other models may be more appropriate. The neutral standing positions for the barefoot and orthotic trials were probably slightly different, and since the neutral positions were the baseline reference points for all kinematic measurements, the measurements for the two conditions may be different. In the future, the neutral standing position differences might be corrected by using offsets measured by X-ray or CT scan. We did not examine the kinematics of the knee, hip, and pelvis, but a consistent effect on the kinematics of the those joints has not been identified with the use of orthoses and merits further study.18 The HAFO is considered effective in controlling excessive plantarflexion while not constraining dorsiflexion, but the 6SF model shows that it may detrimentally constrain forefoot motion. The 6SF model used cannot confirm that the SAFO can control excessive plantarflexion, but the SAFO may still play an important part in increasing gait stability and balance.7 The SMO showed no evidence that it controlled foot inversion at the midfoot joint, and evidence is lacking that the SMO corrects hindfoot or forefoot inversion. The SMO also showed evidence that, like the HAFO and SAFO, it could detrimentally constrain forefoot motion.
Table 3. Significant Differences Between Barefoot and SMO Walking for the Gait Intervals (mean SD, p < 0.01, Difference > 5˚) SMO Joint
Plane
Phase
Barefoot
SMO
p Value
Mean Value
Midfoot Forefoot
S S
ROM
Forefoot
S
ISw PSw ISw MSw TSw LR TSt
8.2 6.2 21.6 6.7 14.2 6.5 10.2 6.4 14.7 4.7 9.6 4.5 15.3 4.4
2.9 5.0 8.1 7.4 2.1 7.4 0.8 8.1 2.6 7.1 3.6 2.6 8.2 2.5
0.002 0.002 0.001 0.001 0.003 0.001 0.001
Variable
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