“…A number of indices have been proposed in the literature to measure gait abnormality, including the Gillette Gait Index (GGI) [23], Gait Deviation Index (GDI) [24] and Gait Profile Score (GPS) [25]. The Gait Profile Score (GPS) [25][26][27] is a well-validated index commonlyadopted as an outcome measure for orthopaedic intervention [11,[14][15][16][17]28]. Thomason et al [14,15] reported improvements in gait and gross motor function at 1, 2 and 5 years post-operatively using a range of gait indices.…”