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February 2007 • Vol. 3, No. 1
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Advancing Orthotic and Prosthetic
Care Through Knowledge
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Mark D. Geil, PhD
Colleen Coulter-O’Berry, PT, MS, PCS
Brian Giavedoni, CP, MBA
This case study describes the results of fitting of an articulating knee component in a child’s first prosthesis with respect to early mobility, crawling, and functional activities. Conventional wisdom suggests that children with limb loss at or above the knee should not receive an articulating knee component in their first prostheses. Some suggest waiting to fit a knee component until the child reaches four or five years of age. New data indicate that children may develop more natural
motor patterns and demonstrate improved biomechanics when an articulating knee is placed in the first prosthesis, sometimes before the first birthday. A 12-month-old was monitored in crawling and functional activities in a biomechanics lab with and without an articulating prosthetic knee. The articulating knee joint improved biomechanical parameters associated with symmetry, efficiency, and typically developing motor performance in crawling and functional activities and is expected to promote more normal ambulation.
Infant and toddlers with limb loss or deficiency who require a prosthetic knee joint present a unique rehabilitation challenge to clinicians. Historically, clinical protocols have placed the goal of stability over the goal of neuromotor development. With a prosthetic knee joint that locks into full extension during locomotion, or no knee unit incorporated in the prosthesis, stability is assured; however, gait deviations to achieve swing-phase clearance are known to develop, and other age-appropriate activities are hindered.1,2 In addition, in past years, prosthetic knee joints were not manufactured in sizes appropriate for infants and toddlers.3,4 Recently, however, appropriately sized knee joints have been developed to allow for flexion and extension during gait. Children’s Healthcare of Atlanta and Georgia State University have investigated the ability of infants and toddlers, 11–36 months, to control prosthetic knee functions during crawling with an articulating prosthetic knee and during age-appropriate activities. The central hypothesis guiding this work is that these subjects will demonstrate knee flexion function paralleling their non-amputee peers if provided with an articulating prosthetic knee at the first prosthetic fitting compared to diminished knee flexion functions if fitted with a non-articulating knee component.
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Figure 1: Transverse plane "overhead view" of crawling at peak contralateral left-knee flexion for articulating and locked prosthetic right-knee conditions. Figures are 3-D reconstructions of the infant’s torso and lower extremities.
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This case study involves a male congenital high right-side unilateral transfemoral amputee. At 12 months of age he received his first prosthesis, which included a modified quadrilateral socket, total elastic suspension belt, Otto Bock 3R38 pediatric prosthetic knee, and SACH foot. The analysis was conducted six days after prosthesis delivery to avoid the development of habitual motor patterns associated with the articulating knee.
Analysis of crawling and functional activities occurred at the Georgia State University Biomechanics Laboratory. Informed
consent was obtained, and the protocol was approved by relevant Institutional Review Boards. For crawling, ten spherical
markers were attached to landmarks on the torso and legs and tracked using eight 120-Hz cameras and Peak Motus software
(ViconPeak, Englewood, Colorado). Crawling trials were recorded with the knee articulating and repeated with the knee
locked into full extension. Markers were removed and functional activities including tall kneel, crawl-to-sit, stair climbing, and climbing and descending a toddler slide were videotaped.
Functional activities were also repeated with the knee locked.
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(Horizontal axis is time in seconds; vertical axis is angle in degrees)
Figure 2: Knee Flexion Angle vs. Time for contralateral left knee during crawling. Top graph shows articulating prosthetic knee condition; bottom graph shows locked knee condition for three crawling cycles. |
Several differences were noted in the crawling patterns when the infant used an articulating knee versus a locked knee. While
locking the prosthetic knee into full extension naturally limited prosthetic knee range of motion, increased motion and excursion was found in other joints. Contralateral knee flexion (Figure 1) increased by more than 18 degrees, perhaps in an attempt to increase step length, since step-through crawling was impossible with the locked knee (Figure 2). Hip abduction also increased in the contralateral limb by 10.9 degrees, a factor that might be associated with increased pelvic motion in the plane of the floor. Trunk motion was also affected, with increased rotation of the shoulders relative to the pelvis. Perhaps most important, crawling velocity was reduced substantially when the knee was locked. Figure 1 shows three complete crawling cycles. In the unlocked condition, the infant completed the cycles in two seconds. When the knee was locked, the infant required five seconds to complete three cycles. The knee flexion patterns for the locked condition reveal hesitation and higher frequency content indicative of an uncertain motor pattern.
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Figure 3: Stair ascent with articulating and locked knee. Infant refused to ascend stairs with knee locked. |
Success in functional activities was reduced when the knee was locked (Figure 3). Several activities that are part of typical toddler development either became biomechanically impossible or were refused by the infant when the knee was locked but were successfully completed with the articulating knee. During other activities, the subject used an abnormal posture or motor pattern to complete the task. For example, tall kneeling was achieved with the knee locked, but the child kneeled on only the contralateral limb, abducting the ipsilateral hip substantially to rest the prosthetic foot to the side.
These results suggest that the inclusion of an articulating prosthetic knee component in perambulatory infants will allow
more normal motor patterns to emerge and will promote success in the development of walking and age-appropriate functional
activities.
Wilk BS, Karol L, Halliday S, Cummings D, Haideri N, Stephenson J. Transition to an articulating knee prosthesis in pediatric amputees. J Prosthet Orthot 1999;11(3):69-74. Giavedoni BJ, Coulter-O’Berry C, Geil MD. The impact of articulated knees on infants and toddlers. American Academy of Orthotics and Prosthetics Journal of Proceedings, 2002. Andrysek J, Naumann S, Cleghorn W. Design characteristics of pediatric prosthetic knees. IEEE Trans Neural Syst Rehabil 2004;12(4):369-378. Cummings D, Kapp S. Lower limb pediatric prosthetics: General considerations and philosophy. J Prosthet Orthot 1992;4(4):196-206.
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