Location of shortening is key factor
By Larry Hand
Contrary to popular perceptions, children with limb length discrepancy (LLD) may each use multiple compensatory strategies when they are walking, depending on where their discrepancy is, and those gait patterns may present a dilemma for practitioners.
In a recent study published in the Journal of Pediatric Orthopedics, Michael Aiona, MD, chief of staff at the Shriners Hospital for Children in Portland, OR, and colleagues found that children can compensate for LLD with multiple gait patterns, depending on which aspect of the limb is shortened.
The researchers used a motion capture system to analyze 45 children (24 girls) with an average age of 12.8 years and an LLD of more than 2 cm and 20 typically developing controls as they walked at a self-selected speed along a two-meter walkway.
Of the 45 children with LLD, 18 used multiple strategies to compensate for the shortening.
- Pelvic obliquity with the short side lower;
- Knee flexion in the longer leg during stance;
- Ankle plantar flexion in the shorter leg through the gait cycle; and
“We looked at a bunch of different kids with a bunch of different causes for differences,” Aiona told LER. “Basically, in some areas they were putting a bit more pressure on certain joints and doing more work in certain areas. They also took different strategies.”
Of the 45 children, four had a diagnosis of Legg-Calve-Perthes, nine had a diagnosis of developmental hip dysplasia, six had growth plate damage due to infection or trauma, five had shortening of the femur, seven had shortening of the tibia, five had syndromes creating limb shortening, and nine had other diagnoses.
Children with a length discrepancy in the femur used compensations at the ankle, which led to more work at the ankle joint on the short limb compared with those in the control group.
Children with tibia shortening demonstrated pelvic obliquity (when the pelvis is lower on the short side throughout the gait cycle), and a few also compensated with knee flexion, which led to more work at the hip on the short limb compared with normal parameters. These findings suggest that underlying factors related to tibial shortening, whether specific to muscles or joints, limit the ankle’s ability to perform increased work, the authors wrote.
Because many clinicians believe that children with LLD who are otherwise healthy develop compensatory strategies specifically to maintain a level pelvis during gait, Aiona and colleagues were surprised to find that 24 children in their study had persistent pelvic obliquity.
“A lot of the kids actually walked with their pelvis uneven, which is a little bit surprising to us,” Aiona said. “There’s some concern whether that has any effects on long-term hip joint development. You could argue that, if hip joint development is affected, then you need to more aggressively manage kids earlier on to get things a bit more equal.”
A lift or surgery may be in order, he said, depending in part on the extent of the discrepancy.
“You could use a lift to equalize, but it’s hard for the kid to play, and you can’t modify every shoe,” Aiona said. “It’s the practicality and the cosmetic things that are involved in it that make it tricky.”
Options for intervention also may be less clear in children who use multiple compensation strategies, which also appears to be associated with the magnitude of the discrepancy. The Shriners study found that all children with shortening of more than 7 cm used multiple compensation strategies. By comparison, only three of 11 children with discrepancies between 4 cm and 7 cm used multiple gait strategies.
“For me, the take-home message is, when the discrepancy becomes greater, that’s when you have to worry more about different ways of how they walk to compensate,” Aiona said.
Mark Geil, PhD, director of the Center for Pediatric Locomotion Sciences at Georgia State University in Atlanta, said the study definitely adds to the evidence base.
“I’ve often taught in my classes that it’s very difficult to predict which strategy an individual will employ given a leg length discrepancy, and in my own lab I’ve found that, when introduced with an acute, artificial leg length discrepancy [eg, shortening a prosthetic pylon], some subjects will immediately adopt multiple strategies before paring down to one over just a few dozen steps,” Geil told LER.
The Shriners findings may provide a new perspective on those observations, Geil said.
“I honestly had not thought of the possibility this paper raises, that LLD etiology might predict gait strategy,” Geil said. “But it makes sense.”
Larry Hand is a writer in Massachusetts.
Aiona M, Patrick K, Emara K, et al. Gait patterns in children with limb length discrepancy. J Pediatr Orthop 2014 Jul 29. [Epub ahead of print]
Geil M, Coulter C. Analysis of locomotor adaptations in young children with limb loss in an early prosthetic knee prescription protocol. Prosthet Orthot Int 2014;38(1):54-61.