Long-term deficits in quadriceps strength and activation following
anterior cruciate ligament reconstruction.
Otzel DM, Chow JW, and
Tillman MD. Physical Therapy in Sport. 2014. [Epub ahead of Print].
Home Message: Following anterior cruciate ligament reconstruction (ACLR)
rehabilitation patients continue to experience muscular strength and stability
deficits in the affected limb compared with the unaffected limb. This is
potentially caused by the loss of neuromuscular control following ACLR and the
rehabilitation process.
The goals of rehabilitation after an anterior cruciate ligament (ACL)
reconstruction (ACLR) are to restore range of motion, strength, and
neuromuscular control. This is done in an effort to return a patient to
pre-injury activity levels. Despite these efforts, we often see long-term
strength deficits in the muscles responsible for dynamic knee stabilization.
Therefore, Otzel and colleagues completed a study to comprehensively analyze
the long-term post-surgical outcomes following ACLR. Twenty-four patients (13
female, 11 male, age ~ 20.2 years of age, ~ 3.3 years post-surgery) who
underwent unilateral ACLR and completed a rehabilitation regime were recruited
for the study. The researchers matched all patients to a control group with
respect to gender, height, and weight. All ACLR patients completed
rehabilitation and returned to recreational physical active. Prior to any
testing all participants completed a 5 minute warm-up on a treadmill. During
each testing session, an investigator measured bilateral thigh circumference. Participants
then completed strength and neuromuscular control testing on a KinCom AP125 dynamometer. All participants
completed 2 sets of 3 trials of maximal effort for knee flexion and extension
movements at 180⁰/s followed by 60⁰/s. After maximum
voluntary contractions were recorded, researchers placed electrodes in a
bipolar configuration over the rectus femoris and vastus medialis. Participants
performed maximal effort isometric knee-extension and as their force output was
steady, the researchers delivered an electrical impulse to assess central activation
deficits of the quadriceps muscles. Overall, knee-extensor strength deficits
and central activation deficits of the quadriceps were detected in the involved
limb compared with the uninvolved limb. Further, no difference in quadriceps
size was found in ACLR patients compared with controls.
Overall, the current
study demonstrates that patients with an ACLR have strength and central activation
deficits. However, the participants with ACLR and control participants had
similar quadriceps size, which indicates that central activation deficits may
be a key issue following ACLR. These deficits could reduce the patient’s
ability to stabilize the joint, which may increase the risk for a new joint
injury or further joint damage. These findings should raise awareness for the
need to continue, and even expand neuromuscular recruitment training throughout
the rehabilitation process. However, we need to identify how long these deficits
persist, if they ever resolve, and if they resolve then the time-frame in which
this is accomplished. This would be a key piece in identifying how intensely
and how often neuromuscular training should continue in the rehabilitation
process or if the rehabilitation process should be lengthened to sufficiently
correct these deficits. Until then, clinicians should look to limit
neuromuscular activation deficits following ACLR and rely more on inter-limb strength
levels instead of muscle atrophy measurements when considering
return-to-activity decisions.
Questions for Discussion: How long in the rehabilitation
process do you have patients work on neuromuscular activation? At what point do
you as a clinicians feel comfortable discontinuing neuromuscular activation
training? Should we teach patients how to promote better muscle activation
after they leave our care so that they can avoid activation deficits?
Written by: Kyle Harris
Reviewed by:  Jeffrey Driban
Related Posts:

Predictors of Failure After ACL Reconstructions

Otzel, D., Chow, J., & Tillman, M. (2014). Long-term deficits in quadriceps strength and activation following anterior cruciate ligament reconstruction Physical Therapy in Sport DOI: 10.1016/j.ptsp.2014.02.003