The locomotory index: a new proposal for evaluating walking impairments

The energy cost of walking per unit of body mass and of distance (Cw) was determined before total hip (n = 17) or total knee (n = 16) arthroplasty and ten days, two, six or twelve months after surgery. The ratio of Cw observed on patients (at the self selected speed) relative to that observed in healthy subjects of the same age at the same speed was defined Locomotory Index (Index Locomotorius, IL). So, IL is a quantitative measure of the economy of walking; for both groups of patients IL amounted to about 1.40 before surgery; it increased significantly 10 days after the operation to 1.86 or to 1.58, for hip or knee patients, respectively. Two, six and twelve months after the operation IL had decreased significantly below presurgery values (1.29, 1.30 and 1.30) for knee replacement, whereas it was still larger, albeit not significantly so, after hip replacement (IL = 1.61; 1.56 and 1.50). It was also observed that the self selected speed increased and the traditional clinical scores (Harris for hip and B.O.A. for knee) improved, with decreasing IL. It is suggested that IL is a useful quantitative tool, in addition to the more traditional clinical scores, for evaluating ambulatory disability in patients.