Can Biofeedback Improve Biomechanical Factors Associated with CAI?

By Seyed Hamed Mousavi, Fateme Khorramroo, Hooman Minoonejad, and Johannes Zwerver

Restoring correct ankle biomechanics is essential for maintaining long-term joint health of the ankle in patients with chronic ankle instability. 

Lateral ankle sprain (LAS) is 1 of the most common musculoskeletal injuries in athletes and the general public. Incomplete recovery and inadequate restoring of function due to lack of appropriate rehabilitation can lead to chronic ankle instability (CAI). Loss of passive ligamentous stability and deficits in neuromuscular control and strength reduce the ability to protect the joint from sudden perturbation, further exacerbating the risk of re-injury. CAI alters normal biomechanics to a greater ankle inversion and laterally deviated center of pressure (COP), thus increases risk of recurrent giving-way of the ankle, ligament sprains, and back pain through changes in the kinematic chain over time. This can also result in abnormal stresses across the talar cartilage (post-traumatic osteoarthritis development). Therefore, restoring correct ankle biomechanics is essential for maintaining long-term joint health of the ankle in patients with CAI.

Biofeedback may alter the biomechanics of lower extremities in patients with CAI. However, no systematic review with meta-analysis reviewing the studies investigating the effect of biofeedback on biomechanical factors associated with CAI has been published. Therefore, this study aimed to systematically review the literature on the effect of gait training and biofeedback on biomechanical parameters in individuals with CAI and conduct a meta-analysis. The research question of this study was: can biofeedback improve biomechanical factors associated with CAI?

Methods

The study authors searched 4 databases including PubMed, Web of Science, Scopus, and Embase from their inception through June 30, 2022. The Downs and Black appraisal scale was applied to assess quality of included studies. Two reviewers screened studies to identify those reporting the effect of biofeedback on biomechanical factors associated with CAI. Outcomes of interest were kinetics and kinematics. Two authors separately extracted data from included studies. Data of interest were study design, number of sessions, intervention, tools, outcomes, number, sex, age, height, and body mass of participants. leading to a total of 13 included studies.

Results

Thirteen studies with a total of 226 participants were included. Biofeedback was capable of shifting COP and lateral plantar pressure medially and reducing foot inversion, adduction, propulsive vertical ground reaction force (vGRF), ankle joint contact force, peak pressure, and pressure time integral in the lateral midfoot and forefoot. Auditory biofeedback had a greater impact on modifying plantar pressure in individuals with CAI. The meta-analyses revealed that visual biofeedback reduces peak pressure in lateral midfoot and pressure time integral at lateral and medial heel and pressure increases under the hallux.

Discussion

The study authors aimed to systematically review the effect of gait training and biofeedback on biomechanical parameters in individuals with CAI. Thirteen studies were included. Three studies assessed visual, 2 assessed auditory, and 1 study assessed both visual and auditory feedback. Two studies assessed a novel device and 5 investigated vibration feedback. The following biomechanical variables were assessed in the included studies: ankle, knee and hip kinematics, plantar pressure, COP, vGRF, joint contact force (JCF), and maximum Force. Moderate evidence suggests that visual biofeedback results in a significant decrease in pressure time integral in lateral and medial heel and significant increase in hallux and decreased peak pressure in total foot and lateral mid-foot. There was no significant difference in pressure contact time and pressure contact area.

There is moderate evidence that visual biofeedback to individuals with CAI is effective in reducing pressure time integral in medial and lateral heel, reducing peak pressure, and in increasing pressure time integral in hallux. All included studies support the use of visual, auditory, haptic, and the novel devices biofeedback during gait and different tasks on lower limb biomechanics in individuals with CAI.

Effect of a gait-training device

Gait training with the novel device decreased pressure on the lateral column of the foot and shifted the COP medially during the stance phase and increased peroneus longus muscle activity with large effect sizes for all comparisons. In comparison, a systematic review assessing the effect of kinesio-taping in individuals with CAI, concluded that kinesio-taping reduces muscle activity of the peroneus longus and range of motion on inversion and eversion. Due to the small sample size and short follow-up, the study authors stated that they cannot speculate on the long-term effects or utility of the gait training device in a clinical setting.

Effect of vibration biofeedback

None of the 5 studies investigated the long-term effect of vibration feedback in individuals with CAI. COP shifted medially in 1 study, but the study was laboratory-based and had a small sample size. Two laboratory-based studies showed significant decrease in joint and ground forces and real-world showed no difference in vGRF loading rate. Vibration feedback can improve gait mechanics in this small sample size after laboratory training but not real-world training. A single session of real-world gait retraining with vibration feedback decreased lateral COP during gait and excessive inversion and adduction during loading response, that are 2 risk factors for recurrent ankle sprains. However, real-world training probably has better frontal plane alterations although a longer training time is required due to practice variability such as changing speed, walking surfaces which improves immediate motor learning outcomes.

Effect of visual biofeedback

Using external biofeedback (the use of laser for feedback comparing to video or mirror) during early phases of task learning and especially when manipulating an automated skill such as walking leads to greater motor learning, retention, and longer lasting improvements. Further refinement for cues or low-cost gait training interventions might be required to modify plantar pressure measures. The results regarding the medial shift of plantar pressure and COP measures in the shoe-mounted laser study are compatible with the suggestions to alleviate lateral COP during walking. Visual feedback with the use of laser is clinically available. In previous studies, 4 weeks of balance training was ineffective at improving inversion/eversion. Kinematics and comprehensive rehabilitation were also incapable of restoring normal gait and specifically targeting the gait is required. The study by Koldenhoven et al proposes that to immediately alter gait biomechanics, a specific training program that addresses the kinematics and kinetics outcomes should be included in standard rehabilitation procedures. It is unclear how long-lasting the effects of visual feedback on ankle inversion angle would be, as the study is lab-based. The shoe-mounted laser technique is clinically available; however, its effectiveness was assessed in a single session of gait training. A previous study examined the effects of midfoot strike gait retraining in healthy individuals, used multiple sessions; no difference was observed in loading rate and in promoting a midfoot strike versus rearfoot strike after removing the visual feedback. In the study by Koldenhoven et al, 8 weeks of kinematic feedback during walking resulted in decreased inversion at initial contact and decreased peak inversion across the entire stance phase. While the Koldenhoven results showed no significant differences in initial contact, these differences can be explained by the timing of the feedback. The visual kinematic feedback was given simultaneously with initial contact, requiring participants to actively adjust their contact for successful outcome. In contrast, the vibration feedback was given later in the gait cycle, allowing participants to make changes only during the loading phase. Changing initial contact with vibration feedback would require transferring the new kinematic pattern without feedback. This transfer likely did not occur after 1 session. Thus, the timing of feedback during the gait phase may affect immediate results, but more research is needed to confirm. However, these changes were not clinically meaningful considering their small percentage changes and effect sizes for the real-time video feedback.

Effect of auditory biofeedback

The auditory biofeedback was effective in reducing plantar pressure on the lateral part of foot and changing the COP medially. The device is available to clinicians but a longer follow-up period is required to support the potential effects on treating patients with CAI. According to evidence, postural control continuously improves when balance training is used along with an external focus of attention. Individuals with CAI relied more on visual stimulus and traditional balance-training programs are not capable of altering the visual reliance.

After evaluating the findings of included studies, it is evident that various forms of biofeedback are able to correct lower limb biomechanics. However, when comparing the different types of biofeedback, it is notable that external feedback achieved better effects on outcomes than internal biofeedback and auditory biofeedback achieved better results in plantar pressure; further investigation is required to determine which mode of external feedback or a multimodal biofeedback is most appropriate in individuals with CAI.

All included studies investigated the young population and many were strongly lab-based. Moreover, according to the results of this study, assessing muscle activity is required in future investigations. Investigations in muscle performance is required in future studies in order to alter gait mechanics in individuals with CAI. To be able to apply results to geriatric practice, future studies should focus on biofeedback systems that facilitate implementation in everyday clinical practice and enable for practicing of tasks that resemble everyday life challenges. Recent progress in technology for wearable, wireless systems to monitor human motion can ease the development of biofeedback systems used in the everyday home environment.

Since all of the assessed biomechanical factors contribute to CAI, investigation on other factors leading to recurrent LAS is recommended.

Conclusion

This systematic review with meta-analysis shows that biofeedback-gait-training has a positive effect on CAI and results in improvement of biomechanical outcomes (ie, plantar pressure, vGRF, JCF, COP, ankle inversion) and leads to a more normal gait pattern. However, more studies are required to support these results and assess long-term effects and clinical consequences of biofeedback or a combination of feedback on CAI in different age groups. Clinicians should consider using low-cost, user-friendly biofeedback devices in order to implement these findings in real-world conditions. By using appropriate feedback interventions, ultimately LAS and CAI can be prevented and/or treated in a more specific way by reducing plantar pressure and ankle inversion angle and improving function of the foot.

Seyed Hamed Mousavi, PhD, is an assistant professor with the Department of Sport Injuries and Biomechanics, Faculty of Sport Sciences and Health, University of Tehran, Iran.

Fateme Khorramroo, MSc sports biomechanics, is associated with the Department of Sport Injuries and Biomechanics, Faculty of Sport Sciences and Health, University of Tehran, Iran.

Hooman Minoonejad, is an associate professor of sport injuries and corrective exercises with the Department of Sport Injuries and Biomechanics, Faculty of Sport Sciences and Health, University of Tehran, Iran.

Johannes Zwerver, MD, PhD, is associated with the Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen, The Netherlands, and with the Sports Valley, Sports Medicine, Gelderse Vallei Hospital, Ede, The Netherlands.