Ankle foot orthoses (AFOs) and foot orthoses have been used routinely for children with cerebral palsy (CP) to obtain heel strike during gait; prevent equinus; improve alignment, balance, and gait efficiency; and prevent deformity.1,2 Orthoses styles and trim lines vary, but almost all AFOs block plantar flexion past 90° to prevent equinus or toe walking and decrease gastrocnemius activity.3 Movement of the forefoot may or may not be blocked in any orthosis and forefoot mobility is usually not described. Forefoot rocker motion is the focus of this article. The purpose is to describe and illustrate how 3 children with spastic CP compensated when they were not able to perform a heel rise because of blocked motion of the digits and forefoot.
THE FOREFOOT ROCKER
Perry was first to describe and name 3 foot movements in gait, which she called “rockers” as they allow the body to progress over the foot and are essential for gait progression.4 The heel rocker, or first rocker, begins at heel strike and ends at foot flat acting as a shock-absorbing mechanism. At initial contact, the ankle is typically at 90°. As the foot hits the ground, the ankle joint typically plantar flexes, which is a motion usually blocked by ankle-foot orthoses. The second rocker, ankle rocker, begins with full foot contact, continues until the tibia and body move forward over the stable foot, and ends at heel rise when the forefoot rocker begins.
The forefoot rocker is the second most important aspect of gait.4,5 At terminal stance, heel rise begins and the forefoot rocker continues until the foot is off the surface. The propulsive phase of gait begins with heel rise and toe extension at the metatarsal phalangeal (MTP) joints, which is also known as a toe break. The joints bend to 55° before the foot is lifted off the ground. Toe extension is critical as it allows the body to move forward over the foot without compensation at other joints.6 Typically when the foot is placed directly in front of the knee, the ground forces cause increased knee extension with less effort than when the foot is placed to the side. This effect is called the plantar flexion/knee extension (PF/KE) couple.7 If the forefoot rocker is blocked, the lever arm of the foot is increased and the child may not be able to move the body over the more strongly extended knee. Therefore, the child may shorten foot length by rotating the foot inward or outward.
The forefoot rocker is the strongest propelling force during the gait cycle and serves to accelerate limb advancement in preswing.5,8 Compensations for a blocked rocker can be detrimental to gait and development.9 Massaad and colleagues10 found the forefoot rocker to be a main gait determinant as it reduces vertical center-of-motion movement and influences the entire gait pattern. The forefoot rocker can be blocked in any ankle or foot orthosis, but blockage is of major significance as the rocker typically provides increased power generation. With free forefoot and ankle rockers, orthoses allow function of the anterior tibialis and calf muscles, which may become stronger and more functional with use.
THE ANKLE-FOOT ORTHOSIS
Solid AFOs (SAFOs) prevent heel rise and toe extension, thus blocking all rockers including the forefoot rocker.11,12 Articulated, or hinged AFOs (HAFOS) usually have a 90° stop to block plantar flexion but allow dorsiflexion so heel rise and digit extension may occur if the MTP joint is not blocked. Thus critical events needed for gait as described by Perry may occur with HAFOs.6
The supramalleolar orthosis (SMO) is an orthotic device that extends just above the malleoli. The SMO may have a full footplate or it may end at or around the MTP joint. It is usually thought to allow free ankle dorsiflexion and may allow free plantar flexion if the back is cut down to allow plantar flexion. Supramalleolar orthoses are not often recommended because they are thought not to control the ankle or block equinus. However, Radtka and colleagues13 found differences of only 1° to 2° degrees in dorsiflexion between SMOs and SAFOs in their study as both orthoses blocked the ankle and forefoot rockers. Dorsiflexion may also have been blocked by plastic extending too high over the top of the foot limiting dorsiflexion and causing the SMO to act as an SAFO.14
Supramalleolar orthoses with free plantar flexion provide stability and control inversion and eversion of the foot. They are recommended for young children, because they can crawl with the foot plantar flexed, get in and out of sitting and rise to standing more easily. Supramalleolar orthoses allow a child to develop an ankle strategy15 as plantar flexion is allowed. Bjornson and colleagues16 found that SMOs improved Gross Motor Function Measure17 scores of young children in all dimensions of the test.
Three children are described in this report. Two had spastic diplegia and could walk independently and one had spastic quadriplegia and used a walker or quad canes to walk. The orthoses in these case studies were all aligned in subtalar neutral. The ankle was neither pronated nor supinated.18 All the children used task-specific electrical stimulation (TASES) before and after receiving the orthoses described here. Task-specific electrical stimulation cannot correct the loss of joint motion resulting from the use of orthoses. Many studies of children with CP mention that children continued to wear their usual orthoses, but unfortunately there is little or no description of the orthoses design and fit or how they affect gait.5 This makes it very difficult, if not impossible, to compare one study with another when orthoses are used. Only in case 3, below, are outcomes described after the fit of the orthoses was corrected and TASES was again continued.
This 4-year-old child with spastic diplegia, Gross Motor Function Classification System (GMFCS) Level II,19 came to the clinic for the purpose of obtaining orthoses to correct his gait that was characterized by foot pronation and equinus. Later at the age of 6 years, he returned to obtain new SMOs as he had grown. The new SMOs had the same prescription as the previous orthoses, with the back cut down to allow full plantar flexion and the polypropylene foot plate ending at the metatarsal joint with foam continuing to the end of the digits. However, the new SMOs (Figure 1) had the same foot plate as the old SMOs except for the lateral plastic trim that extended distal to the metatarsal heads. When the SMOs were first put on the child, he became more hyperactive than usual. The plastic gave the orthoses some spring, which he enjoyed as he began to bounce about the room, lifting his body up with each step. He waved his arms apparently to give more spring to the step. He walked on his toes with excessive hip and knee flexion and some internal rotation of the legs (Figure 2A). The solution was for the physical therapist to remove the small triangular area of plastic that extended past the metatarsal heads on the lateral sides of the orthoses. Dotted lines in Figure 1A and 1B show the SMO cut location, before and after being cut. About half an inch of plastic trim distal to the metatarsal heads (Figure 1C) was removed. After removing the material from one SMO, the child walked again to allow gait changes to be observed. He attempted more bouncing, but this time he was not successful and he remained flat-footed and immediately became less hyperactive and stopped waving his arms. The second SMO was then corrected and he walked flat-footed with increased knee extension in mid-stance (Figure 2B). Removing only a small amount of material blocking the forefoot rocker (Figure 1C) made a significant change in plantar flexion and internal hip rotation as well as overall hyperactivity. The change was probably due mainly to his inability to keep the weight back over the feet, which helped his balance.
This 6-year-old girl with spastic quadriplegia, GMFCS Level II (Figure 3), had progressed from HAFOs to SMOs the previous year. The SMOs had a full plastic sole to the end of the toes and trim lines to give her free plantar flexion with no rockers blocked. She walked flat-footed in the SMOs intermittently or when reminded. The SMOs corrected her pronation. When they were outgrown, a new pair with the same prescription was ordered. Full plantar flexion was still possible, as the first and second rockers were not blocked. However, as with case 1, the lateral sides of the new pair extended very slightly distal to the metatarsal heads, which was not initially noticed. She walked only a few steps before falling quickly to the floor. She got up and walked with 1 hand on, or barely touching, the wall for balance as she walked on the toes of both feet (Figures 3A and 3B). Again the lateral sides of the SMO were removed as in case 1. The sole was untouched, only the distal ends of the lateral sides were cut similar to that shown in Figure 1C. Without the forefoot rocker blocked, she was then able to walk flat-footed on either foot and did not fall (Figure 3C and 3D). Balance was improved as seen by the lowering of the arms.
This 4-year, 11-month-old child with spastic diplegia was classified as GMFCS Level III. His physician recommended selective dorsal rhizotomy because of a crouched gait. At the time he came to the clinic, he walked independently with a walker or quad canes while wearing HAFOs, which did not block the ankle or forefoot rockers. In addition to orthotic modification, TASES was used. This is a technique in which muscles that are typically active during the task are electrically stimulated using a handheld remote switch activated at the appropriate times within the task.20 After outgrowing his HAFOs, new HAFOs arrived with an unexpected design change. The ankle of the left orthotic device had a 3° dorsiflexion stop and the right had a 6° stop (Figure 4A), which forced him to stand in a crouch since the HAFOs were positioned in dorsiflexion. Standing in the HAFOs with a vertical tibia was impossible. Bilaterally, the forefoot rocker was totally blocked by stiff lateral plastic sides extending distal to the metatarsal head and over the first toe (Figure 4A, medial sides shown). A heel rise was impossible. The blocked ankle rockers were corrected to a 90° stop (Figure 4B) and the child was lightly held to see how he could walk in the HAFOs with only the heel and forefoot rockers blocked. Because he was unable to use a heel rise and move his body over the plantigrade feet, he compensated by internally rotating the legs bilaterally to decrease the foot length, thus making it easier to move his body forward (Figure 5A) over the foot.7 The forefoot rockers were unblocked by cutting back the excessive plastic. Dotted lines (Figure 4B) show where the forefoot rocker HAFO block on the right was cut back; the left side was not yet cut back when the photo in the figure was taken. With a free forefoot rocker on both HAFOs, the knee extension couple was not as strong as the foot lever arm was decreased. He was able to walk with the same light assistance for balance, but he no longer internally rotated his legs (Figure 5B). He had heel rise and was better able to move the body over his feet. This gait change is frequently seen in this clinic when the forefoot rocker is unblocked.
The boy then had a chance to develop and learn to walk without aids. He continued with his physical therapy program, which used orthoses without blocking the ankle or forefoot rockers, and TASES to activate needed muscles, regardless of spasticity.20,21 Respond Select (EMPI Corp, Henderson, Nevada) and Neuro Rehabilicare's NT200 (Rehabilicare, New Brighton, Minnesota) were used but are no longer available. As his muscles became more active and stronger with TASES and joint mobility of the orthoses allowed the muscles to function, the boy made clinically significant progress by changing GMFCS Level (Level III to Level II) long after the age when children with CP generally have begun to regress.22 Russell and colleagues23 found that no child older than 5 years at GMFCS Level III was able to change levels. Seventy-three percent do not change GMFCS levels.24 Progress in this case is clinically and medically significant.25Figures 6A and 6B show his progress in gait just before his GMFCS level change, and Figures 6C and 6D show his gait after the level change at the age of 9 years. Figure 7 records his progress on Gross Motor Function Measure. He received no surgery during this period.
Forefoot rockers in all AFOs may be easily blocked. The children described here compensated for the blocked rocker by internally rotating the legs, walking in equinus, and falling. Internal rotation of the hips is a very complicated subject. Orthoses that block the forefoot rocker are not listed as a cause for internal hip rotation.26 Recommendations in the literature report that the best, if not the only, way internal rotation can be corrected is with surgery.27 However, O'Sullivan et al28 caution that since it is difficult to identify the cause of internal rotation, the treatment is often unclear and outcomes are unpredictable and sometimes unsatisfactory. The findings from these cases suggest that bilateral orthoses should be listed as another cause of internal hip rotation. If only one side is blocked, that leg often externally rotates and the child does not shift weight adequately to that side. The leg is used more as a “peg leg.”
Both children described in cases 1 and 2 received new SMOs with free plantar flexion but with blocked forefoot rockers. Although both children were classified at GMFCS Level II, the child in case 2 had spastic quadriplegia and more motor involvement, which could explain why she also had loss of balance when the forefoot rocker was blocked. Figure 3B shows the child described in case 2 walking flat-footed with forefoot rocker unblocked without hand support and with her arms lowered. The child described in case 1 had spastic diplegia and more muscle control and so his compensation allowed him to enjoy bouncing on his toes without falling. He also compensated with slight internal hip rotation before the SMOs were corrected. Both children had immediate positive changes in gait when small pieces of plastic trim, which blocked digit extension, were removed. The orthoses of the child described in case 3 had a large amount of plastic over the toes for which he compensated with internal hip rotation until the blockage was removed. For the children in cases 1 and 2, plantar flexion was available and they each had enough strength to walk on their toes and maintain the PF/KE couple. The child in case 3 did not have plantar flexion available and needed to rotate the leg, reduce the PF/KE couple, and shorten the foot lever length.
Both children in cases 1 and 2 responded to the blocked forefoot rocker with excessive knee and ankle extension after mid-stance. This excessive knee extension and plantar flexion seems similar to the concern that Buckon and colleagues12 expressed in their 2004 study of children with spastic diplegia walking barefoot or wearing various orthoses. They reported that some children with spastic diplegia at GMFCS Level II had an increase in knee extension in early stance. It appears that those in GMFCS Level I did not have this problem, perhaps because they were more developed than those at Level II. Buckon and colleagues12 felt that the excessive knee extension was detrimental for those at Level II because of the mobile ankle joint and they reversed their previous recommendation of using the HAFO over the SAFO. They concluded that one should constrain ankle movement in some children who walked on their toes. However, all their AFOs had the forefoot rocker blocked with extended trim lines and this blockage may have caused the excessive knee extension rather than the ankle hinge. These compensations over time may have become permanent and may not have been a result of the initial brain lesion but a result of the orthoses.
Very small differences in the trim lines of foot orthoses may significantly and negatively affect gait of a child with CP. Since published studies do not describe the orthoses in detail, it is very difficult, if not impossible, to compare studies. It is critical that those doing research evaluate the influence of all foot and ankle orthoses used, even if the purpose of the study is focused on gait alone and not on orthoses. Perhaps the outcomes from managing CP could be more favorable than currently shown if orthoses did not totally block spastic muscles action and these muscles were allowed to develop. It should be the responsibility of the physical therapist to evaluate all orthoses used by their clients as the child spends much time with the physical therapist. The therapists should then communicate problems to the physician and the orthotist.
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