The Effect of Anterior Cruciate Ligament Reconstruction on Stride-to-Stride Variability

Purpose

The purpose of our study was to investigate the functional outcome after anterior cruciate ligament (ACL) reconstruction using bone–patellar tendon–bone (BPTB) and quadrupled semitendinosus and gracilis tendon (ST/G) autografts by evaluating stride-to-stride variability.

Methods

Six patients with BPTB and 6 patients with STG ACL reconstruction, 2 years postoperatively, and 6 healthy control subjects walked on a treadmill at a self-selected pace while 2 minutes of continuous kinematic data were recorded with a 6-camera optoelectronic system. Stride-to-stride variability was calculated from the knee flexion/extension data using the nonlinear measure of approximate entropy, which estimates the regularity of movement patterns over time.

Results

ACL reconstruction affects stride-to-stride variability. Both the BPTB and the ST/G groups had significantly larger approximate entropy values than the healthy controls. No differences were found between the BPTB and the ST/G approximate entropy values.

Conclusions

After ACL reconstruction using either BPTB or quadrupled ST/G, there is increased gait variability as compared to healthy individuals. This could be caused by the altered neuromuscular activity found in ACL-reconstructed limbs.

Level of Evidence

Level III, case control study.

Key Words: Anterior cruciate ligament reconstruction, Approximate entropy, Bone–patellar tendon–bone autograft, Motion analysis, Quadrupled semitendinosus and gracilis tendon autograft