Effects of a corrective heel lift with an orthopaedic walking boot on joint mechanics and symmetry during gait

Abstract

Background: Orthopaedic walking boots are commonly prescribed following injury and surgery. The boot creates a leg length discrepancy which is thought to affect limb symmetry and gait mechanics. This study aimed to examine the effects of a corrective heel lift for the contralateral limb on the mechanics and symmetry of walking with an orthopaedic walking boot.

Research question: Does a corrective heel lift reduce biomechanical alterations and asymmetries caused by an orthopaedic boot during gait?

Methods: Healthy males (n=17) walked with normal shoes (Shod), an orthopaedic boot (Boot), and a corrective heel lift on the contralateral limb to the boot (Lift). A 10-camera motion capture system (Vicon, 100Hz) and four force platforms (AMTI, 1000 Hz) recorded lower extremity biomechanics. Pairwise statistics tested for differences in hip and knee kinematics and kinetics, and a symmetry index quantified limb symmetry.

Findings: The Boot affected the sagittal and frontal plane hip mechanics and transverse plane knee mechanics (p<0.05), and increased the asymmetry compared to the Shod condition. The Lift improved the symmetry of some measures but increased the frontal plane hip asymmetry compared to the Boot. However, introducing the Lift did not change all kinematic variables affected by the boot.

Significance: The Lift reduced some of the asymmetries introduced by the Boot, but also introduced new asymmetry in the hip frontal plane motion. The leg length discrepancy caused by the boot is probably not the only cause of altered gait mechanics. Prescribing a heel lift to a patient with an orthopaedic walking boot should be based on the individual patient's needs.

Keywords: Biomechanics; Brace; Gait; Orthopedics; Rehabilitation.

Fig 1.

The orthopaedic boot used for the study with reflective markers attached (Aircast, BetterBraces, Canada).

Fig 2.

Hip joint motion. The overall ROM of the hip for the three conditions across the three planes of motion. Statistical symbols next to the axis label indicate a difference in the overall ROM, symbols next to the graph indicate differences in the motion in the direction of the bar. *indicates a significant difference compared to the Boot condition at p<0.05, †indicates a large effect size compared to the Boot condition at Cohen’s D>0.8

Fig 3.

Knee joint motion. The overall ROM of the hip for the three conditions across the three planes of motion. Statistical symbols next to the axis label indicate a difference in the overall ROM, symbols next to the graph indicate differences in the motion in the direction of the bar. *indicates a significant difference compared to the Boot condition at p<0.05 †indicates a large effect size compared to the Boot condition at Cohen’s D>0.8

Fig 4.

Symmetry bar graphs indicating the degree of asymmetry between the limbs during the three conditions in the three planes of motion in both the hip and the knee.