Conditioned patellar tendon-tap reflexes in patients with ACL reconstruction

Area of Science:

• Neuroscience
• Orthopedics
• Sports Medicine

Background:

• Anterior cruciate ligament (ACL) reconstruction is a common orthopedic procedure.
• Patients often experience persistent quadriceps strength deficits after ACL reconstruction.
• The impact of ACL reconstruction on neuromuscular control, specifically stretch reflexes, requires further investigation.

Purpose of the Study:

• To investigate the effects of ACL reconstruction on patellar tendon-tap stretch reflex responses.
• To compare reflex profiles between the ACL-reconstructed leg and the contralateral healthy leg.
• To determine if conditioning intervals influence reflex responses in individuals post-ACL reconstruction.

Main Methods:

• Six neurologically healthy subjects with ACL reconstruction participated.
• Patellar tendon-tap reflexes were assessed using a custom apparatus.
• Measurements included peak isometric force, contraction time, and EMG of the rectus femoris.
• Unilateral and conditioned reflexes (25 ms, 75 ms, 150 ms intervals) were evaluated.
• Kruskal-Wallis nonparametric analysis of variance was employed due to the small sample size.

Main Results:

• All subjects exhibited quadriceps strength deficits in the ACL-reconstructed leg compared to the contralateral leg.
• Stretch reflexes were facilitated at long-latency conditioning intervals (75 ms, 150 ms) and inhibited at short-latency (25 ms) for both legs.
• No significant differences were found in conditioned or unilateral stretch reflex profiles between the ACL and non-ACL legs.

Conclusions:

• ACL reconstruction results in significant quadriceps strength deficits.
• Despite strength deficits, unilateral and conditioned patellar tendon-tap reflex profiles remain unaltered after ACL reconstruction.
• Neuromuscular reflex pathways may compensate or be resilient to the changes induced by ACL reconstruction.