Long-term follow-up after patellar tendon shortening for flexed knee gait in bilateral spastic cerebral palsy

Flexed knee gait is a common gait dysfunction in individuals with bilateral spastic cerebral palsy (BSCP) and is often addressed with single event multilevel surgery (SEMLS). SEMLS has been shown to have positive short-term effects especially on sagittal knee joint kinematics with less knee flexion during stance phase. However, mid- and long-term observations are rare, and results are reported in discrete parameters or summary statistics where temporal aspects are not considered. Does the improved knee joint kinematics after patellar tendon shortening (PTS) as part of SEMLS persist in the long-term in individuals with BSCP? Data of instrumented gait analysis of twelve participants (females/males: 5/7, mean age: 15.3 ± 3.4 years) with BSCP treated with PTS as part of SEMLS were retrospectively analyzed. Participants had had follow-up gait analysis 1, 5 and 7 years or more after surgery. Three-dimensional lower extremity kinematics of walking at a self-selected speed were collected using a 12-camera motion capture system and 4 embedded force plates. One-dimensional statistical parametric mapping (SPM) was used for data analysis, permitting time point comparisons of continuous data. Time point comparison revealed no significant differences in the sagittal plane for knee joint kinematics (p > 0.05) over the tree measurement time points. Hip and ankle joint kinematics as well as normalised walking speed remained stable over the observation period. This is the first study investigating lower extremity kinematics in patients with BSCP and flexed knee gait after SEMLS with SPM. Results demonstrate that positive effects on sagittal knee joint kinematics of PTS as part of SEMLS persist up to 9 years after surgery and progressivity does not reoccur. Thus, if clinical examination indicates an operation in individuals with BSCP, improved kinematics through SEMLS persist into adulthood. With the relatively new statistical procedure SPM gait can be displayed and analysed in established joint angle curves making them easier to understand (e.g. physiotherapists, movement scientists, physicians).