Kinematics identify subgroups of kids with CP and equinovarus

Chicago researchers have identified clinically relevant subgroups based on foot and ankle kinematics in children with equinovarus secondary to hemiplegic cerebral palsy (CP) that could help improve treatment planning and clinical outcomes.

By Barbara Boughton, Lower Extremity Review May 2015

The researchers used gait analysis and multisegment foot and ankle modeling to classify 24 children with hemiplegic CP, all of whom had a clinical diagnosis of unilateral equinovarus, and 20 typically developing children into five subgroups.

“There is a lot of variability in characteristic foot deformities among children with equinovarus secondary to hemiplegic cerebral palsy,” said lead author Joseph Krzak PT PhD PCS, assistant professor of physical therapy at Midwestern University in Downers Grove, IL, and senior motion analysis laboratory physical therapist at the Shriners Hospital for Children in Chicago. “As a result of this variability, as well as multiple combinations of surgeries used to correct equinovarus, there is a lot of variability in treatment outcomes.”

In fact, postoperative success rates range from 67% to 82% for surgeries aimed at correcting equinovarus in hemiplegic CP, the researchers noted in their paper, which was published in the February issue of Gait & Posture.

“Hopefully our research could be used to improve outcomes, since children with similar foot deformities are likely to benefit from similar surgical interventions,” Krzak said.

The researchers used the Milwaukee Foot Model, which employs radiographic skeletal indexing, to measure and quantify the 3D kinematics of small foot segments during locomotion. Five gait classifications for the children in the study were developed using principal component analysis and cluster analysis.

One subgroup of 15 typically developing children and three children with CP, all of whom had a rectus foot type with a well-aligned hindfoot and forefoot, served as a control group. Four other subgroups were classified according to the presence or absence of equinovarus deformities: those with just hindfoot involvement, both hindfoot and forefoot involvement, varus deformity with hindfoot and forefoot involvement but no equinus, and forefoot adductus but no hindfoot varus or equinus.

In the subgroup without equinus or varus, the chief complaint for patients with CP was the in-toeing often seen in that patient population—which can come from internal rotation of the trunk, pelvis, hip, lower leg, hindfoot, and/or forefoot, Krzak said.

“Although equinovarus deformity may have contributed to a chief complaint of in-toeing, the deformity at the foot and ankle may have been only a small contributor,” he said.

Eventually, the gait classifications developed in the study could be used, not only for treatment planning, but also to evaluate the outcomes of surgery.

“Right now the assessment of surgical outcomes is observational,” Krzak said. “But, if the subgroup classifications we develop are validated in future studies, they could be used to quantitatively measure the outcomes of surgery.”

The next step for the researchers is to validate their findings in a larger group of 100 children with equinovarus secondary to hemiplegic CP; that study is currently being planned, Krzak said.

Krzak acknowledged that the technology used in the study was quite sophisticated and not available to most practitioners.

“One future direction of our research could be to show how clinical tools that most clinicians have access to could be used to classify and assess children based on the subgroups we identified,” he said.

The study by Krzak and colleagues provides insight into the variability of foot deformities that exist in equinovarus secondary to hemiplegic CP, said Susan Rethlefsen PT DPT, a physical therapist at the motion analysis laboratory at the Children’s Orthopaedic Center in Los Angeles, whose work centers on assessing children with CP who are candidates for surgery.

“The study’s findings do verify what I see clinically in terms of the different types of deformities,” Rethlefsen said.

It is difficult to look at an equinovarus foot and assess just where the deformity arises, she acknowledged.

“This study takes us one step closer to being able to measure that accurately,” Rethlefsen said.

Although most of the deformities in the study were fairly severe—since all the children with CP were candidates for surgery—the subgroup classifications could also be used for less severe cases and for nonsurgical treatment planning, Krzak said.

Rethlefsen concurred.

“Knowing the characteristics of a foot deformity could help an orthotist position the foot correctly during casting,” she said.

Barbara Boughton is a freelance medical writer based in the San Francisco Bay Area.

Source Lower Extremity Review

Kinematic foot types in youth with equinovarus secondary to hemiplegia, Joseph J. Krzak, Daniel M. Corcos, Diane L. Damiano, Adam Graf, Donald Hedeker, Peter A. Smith, and Gerald F. Harris. Gait Posture. Author manuscript available in PMC 2015 Sep 18. Published in final edited form as: Gait Posture. 2015 Feb; 41(2): 402–408. Published online 2014 Nov 10. doi: 10.1016/j.gaitpost.2014.10.027