Accuracy of partial weight bearing after autologous chondrocyte implantation

Objective:To determine whether patients can accurately replicate and retain weight-bearing restrictions in both stationary (static) and dynamic conditions after autologous chondrocyte implantation (ACI).Design:Case series.Setting:Rehabilitation clinic.Participants:A consecutive sample of patients (N=48) who had undergone ACI to a medial or lateral femoral condylar defect in the knee.Interventions:Patients were trained to partially weight bear using bathroom scales and forearm crutches prior to assessment.Main Outcome Measures:A force platform was used to measure peak vertical ground reaction forces in patients during static and dynamic conditions immediately after weight-bearing instruction and training, and again during gait 7 days after training.Results:Immediately after instruction and weight-bearing practice on a set of scales, patients exerted a mean of 15.8% body weight more than expected during walking for 20% weight-bearing trials, 8.3% more for the 40% trials, 11.9% more for the 60% trials, and 1.2% less for the prescribed 80% trials. Accuracy of weight-bearing replication improved across all weight-bearing levels when assessed 7 days later, when patients exerted a mean of 6.6% body weight more than expected during walking for 20% weight-bearing trials (9.2% body weight improvement), 4.2% more for the 40% trials (4.1% body weight improvement), 9.9% more for the 60% trials (2% body weight improvement), and 0.2% more for the 60% trials (1% body weight improvement).Conclusions:Patients were unable to follow weight-bearing restrictions after instruction and practice on a set of scales, and patients were unable to replicate weight-bearing levels in both static and dynamic conditions.