Sports Medicine Research: In the Lab & In the Field: The Effects of Neuromuscular Training on the Gait of ACL-deficient Patients (Sports Med Res)


Monday, December 5, 2011

The Effects of Neuromuscular Training on the Gait of ACL-deficient Patients

The Effects of Neuromuscular Training on the Gait Patterns of ACL-deficient Men and Women

Di Stasi SL, Snyder-Mackler L. Clin Biomech (Bristol, Avon). 2011 Nov 5. [Epub ahead of print]

After anterior cruciate ligament (ACL) rupture in the US the most common plan of treatment is to undergo reconstruction. Typically, the better the functional level of the patient before surgery, the better the outcome after surgery. Neuromuscular training has been implemented for athletic individuals to prevent ACL injury, to enhance performance, and to improve movement deficiencies throughout rehabilitation. Perturbation (PERT) training is a neuromuscular training program that involves the manipulation of unstable surfaces in both unilateral and bilateral stance positions. It has been implemented prior to ACL reconstruction (ACLR) in an attempt to improve functional status going into surgery [Fitzgerald, 2000]. It has been documented that individuals who receive PERT training before surgery compared to those who received strengthening alone, at 6 months after ACLR demonstrate decreased gait deviations [Hartigan, 2009]. However, these variations have not been evaluated based on gender and have not been examined immediately before and after PERT training. Therefore the purpose of this study was to evaluate gait patterns before and after PERT training in ACL-deficient men and women that are within 7 months of their initial injury. It was hypothesized that men and women would respond differently to the training intervention and this would be observed through gait variables. Gait kinematics and kinetics were recorded with motion capture systems before and after a standard 10 PERT training sessions. Before training, the involved limbs of women demonstrated decreased hip and knee flexion angles and moments at peak knee flexion during gait compared to their own uninvolved limb as well as both limbs of men. Women also demonstrated decreased knee excursions and increased hip excursions compared to men during early stance phase. Prior to training, men only demonstrated knee extensor moment deviations compared to their uninvolved limb. After training, a more symmetrical gait pattern was seen for women between involved and uninvolved limbs. The only deviations that persisted were knee extensor moments between limbs of both men and women.

It is well known that women demonstrate different movement patterns than men that put them at higher risk for ACL injury, which include increased knee valgus angle and increased forces during landing tasks [Hewett, 2000]. This study demonstrated that after ACL injury and before surgery, women move differently than men. This intervention of PERT training also demonstrated the ability to decrease these abnormal gait patterns in women and this symmetrical gait pattern has been found to be maintained at 6 months after surgery compared to those who only received strength training [Hartigan 2009]. Yet the bigger questions still remain. What do these gait deviations mean for our patients? Do fewer gait deviations mean higher function? Improved athletic ability? Lower rate of re-injury? Lower incidence of OA? This study provides continued support for gender differences in athletes with ACL injuries, however we are still unable to predict if these early gait abnormalities influence the long term results of these individuals.

Written by: Kathleen White
Reviewed by: Stephen Thomas

Related Posts:
Predictors of Self-Reported Knee Function in Nonoperatively Treated Individuals with ACL Injury

Di Stasi SL, & Snyder-Mackler L (2011). The effects of neuromuscular training on the gait patterns of ACL-deficient men and women. Clinical Biomechanics (Bristol, Avon) PMID: 22061048


Dustin Grooms said...

Great write up and thanks posting!

Why do you think PERT training had minimal to no effect on the gait of the male participants? They still had the same knee extensor moment asymmetry correct? Along those lines why did it also remain unchanged for females? It would seem that knee extensor moment would be a factor influencing ACL risk? Is the lack of change with only PERT training concerning or indicate other interventions should be recommended as well as PERT training?

Kathleen White said...

Thanks for your comment Dustin. You made some great points and posted some challenging questions.

Before the PERT training, males demonstrated minimal gait asymmetries, with only knee extensor moments at peak knee flexion being different between their limbs. I believe that this lack of asymmetry before training contributed to the lack of change after training, unlike the females response. The females demonstrated more asymmetries and in turn had more room for improvement- if you will.

Both before and after PERT training, males and females continued to demonstrate asymmetrical knee extensor moments at peak knee flexion. These knee moments appear to be unchanged from PERT training. If there subjects were followed after ACL-reconstruction and long term and continued to demonstrate asymmetrical moments at the knee there is concern for overloading of the joint. This is thought to contribute to joint degeneration and ultimately osteoarthritis.

However, this study was just to evaluate the intervention of PERT training in males and females before surgery and the effect on gait biomechanics. From this research it is unclear that having knee extensor asymmetries before surgery is problematic. More research should be conducted to follow these individuals long term.

Stephanie Di Stasi said...

Kathleen and Dustin,

I appreciate the review and the great comments on our article.

Kathleen, you definitely hit on the big reason we believe there was a ‘lack of effect’ of perturbation training – our male non-copers moved more symmetrically than the females following injury. This was not completely unexpected. We know that women are more likely to be classified as non-copers (ACL-deficient athletes who often have recurrent knee instability and significantly reduced function), and other, recent publications (Ageberg 2010, Ardern 2011) indicate that women demonstrate poorer function before and after ACL reconstruction when compared to men. So, we hypothesized that women’s gait mechanics might also reflect these reported functional deficits.

Our data, albeit on a small cohort of athletes, underscores three main points: (1) gait mechanics of male and female non-copers appear unique following injury, and women demonstrate more pervasive asymmetries, (2) female non-copers demonstrated a positive response to perturbation training by way of improved symmetry, and (3) asymmetrical knee extensor moments persist six months after surgery despite this pre-operative neuromuscular training. The last finding is consistent with previous reports (Devita 1998, Hart 2010, Roewer 2011, Timoney 1993), and is of great concern. Paterno and colleagues wrote two articles that not only document persist vGRF asymmetries (2007) and knee extensor moment asymmetries (2010) at least one year after ACLR, but that these asymmetries are a significant factor in a very sensitive and specific predictive model for secondary ACL injury (Paterno 2010).

It’s pretty clear that we have a lot to learn about the relationship of gait asymmetries and reduced function to the initiation and progression of osteoarthritis. Certainly, the most immediate concern are the FRIGHTENING reinjury rates that are being reported in this population – I think we’ll be seeing a lot more papers looking at post-operative care guidelines for ACL-reconstructed athletes!

Thanks again for the comments – this is a great forum!

Stephanie Di Stasi, PT, PhD
Post-doctoral Researcher
The Ohio State University

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