Bilateral spatiotemporal postural control impairments are present in participants with chronic ankle instability

Highlights

• Deficits in postural control are associated with CAI.

• The Lateral Step-Down Test was completed on both limbs to assess postural control.

• Center of pressure measures did not reveal any significant differences in postural control.

• Spatiotemporal postural control deficts were found in individuals with CAI on both limbs.

Abstract

Objectives

This study evaluated center-of-pressure (COP) and time-to-boundary (TTB) measures of postural control during a Lateral Step-Down Test in participants with chronic ankle instability (CAI).

Design

Cohort study.

Setting

Biomechanics laboratory.

Participants

Physically active adults with CAI (n = 15) and matched controls (n = 15).

Main outcome measures

Traditional COP and TTB measures of postural control were computed in the medial/lateral (ML) and anterior/posterior (AP) directions.

Results

No significant results were found for the traditional COP measures (p > 0.05). The CAI group exhibited a lower TTB ML absolute minimum on their affected limb compared to the matched limb of the control group (p < 0.001). Additionally, on average the CAI group displayed significantly lower TTB ML mean of minima (p = 0.004) and TTB standard deviation of minima in the ML (p < 0.001) and AP directions (p = 0.002) regardless of limb.

Conclusions

Sensorimotor impairments associated with CAI negatively alter spatiotemporal postural control and may cause a maladaptive reorganization of centrally mediated motor control strategies that results in bilateral postural control deficits during the Lateral Step-Down Test. In addition, traditional COP measures did not reveal any postural control deficits suggesting that a spatiotemporal analysis should be used when assessing postural control in participants with CAI.

Introduction

Despite extensive research examining the mechanisms and treatment of lateral ankle sprains over the last several decades, this injury remains the most common musculoskeletal injury sustained in athletics and the general population (Doherty et al., 2014a). A low percentage of individuals (∼30%) will return to high-level activity without any residual impairments following a lateral ankle sprain (McKay, Goldie, Payne, & Oakes, 2001), and consequently, the vast majority (∼70%) will experience recurrent injuries (van Rijn et al., 2008), persistent pain and swelling (Hertel, 2000), decreased self-reported physical activity (Hubbard-Turner, Turner, Burcal, Song, & Wikstrom, 2018), and a continuum of sensorimotor and mechanical impairments following the initial injury (Hertel, 2008). Similarly, these factors have been suggested to contribute to the complex spectrum of long-term joint dysfunction, or chronic ankle instability (CAI), resulting in subjective feelings of ankle joint instability and/or episodes of the ankle giving way leading to recurrent injuries (Hertel, 2002; Tanen, Docherty, Van Der Pol, Simon, & Schrader, 2014).

Postural control deficits are frequently reported following an acute lateral ankle sprain (Doherty et al., 2015a; Wikstrom et al., 2010a, Wikstrom et al., 2010b) and in individuals with CAI (Hertel & Olmsted-Kramer, 2007; Hoch, Staton, McKeon, Mattacola, & McKeon, 2012), suggesting that poor postural control is one contributing factor to the CAI paradigm. Unilateral weight-bearing exercises such as the Star Excursion Balance Test (SEBT) and the Lateral Step-Down Test are commonly used clinical tests to evaluate dynamic postural control and lower extremity injury potential (Claiborne, Armstrong, Gandhi, & Pincivero, 2006; Gribble, Hertel, & Plisky, 2012). Performance on the SEBT in individuals with CAI has been extensively evaluated in the literature with reports of reductions in reach distance, most notably in the anterior direction (Doherty et al., 2016a, 2016b; Hoch et al., 2012; McCann et al., 2017). The impairments in dynamic postural control often result from the underlying sensorimotor impairments associated with CAI (Hertel, 2008), but recent evidence indicates that mechanical impairments are also contributing factors to poor dynamic postural control during the SEBT (Hoch et al., 2012). Moreover, studies that evaluate other types of dynamic unilateral weight-bearing exercises in participants with CAI have also identified significant alterations to lower extremity movement mechanics during gait (Moisan, Descarreaux, & Cantin, 2017) and jump-landings (Simpson, Stewart, Macias, Chander, & Knight, 2018), as well as a proximal to distal joint movement strategy resulting in reduced dynamic postural control (Gribble & Robinson, 2009).

The Lateral Step-Down Test is a clinical measure that requires coordination of multiple lower limb joints, neuromuscular control, strength, pelvic stability, and adequate range of motion (Claiborne et al., 2006). Although this assessment has been shown to detect lower limb movement impairments in individuals with CAI (Grindstaff, Dolan, & Morton, 2017), the resultant postural control strategies exhibited while performing the Lateral Step-Down Test in individuals with CAI are currently unknown. Quantifying the rate and magnitude of center of pressure (COP) excursions is the most common method of assessing postural control, but recent evidence suggests that traditional COP measures may not adequately detect postural control deficits in participants with CAI (Hertel & Olmsted-Kramer, 2007; Hertel, Olmsted-Kramer, & Challis, 2006; Wikstrom et al., 2010b; McKeon and Hertel, 2008a, McKeon and Hertel, 2008b). Time-to-boundary (TTB) is a spatiotemporal analysis that estimates the time it would take the COP to reach the limits of the base of support if the COP trajectory were to continue with its instantaneous directional velocity (Hertel et al., 2006). Lower TTB indicates an individual has less time to execute a postural correction in order to preserve the COP within the boundaries of the base of support, resulting in greater postural instability. Additionally, TTB measures have been shown to be poorly correlated with traditional COP measures and research suggests that TTB measures are a more sensitive measure to detect postural control deficits in individuals with CAI (Hertel et al., 2006; Hertel & Olmsted-Kramer, 2007).

Recent studies have examined traditional COP excursions during the SEBT in healthy (Keith, Condon, Phillips, McKeon, & King, 2016) and CAI populations (Jaber et al., 2018), which enhance the understanding of the sensorimotor and mechanical constraints that contribute to poor dynamic postural control. However, a lack of consistency detecting postural control deficits using traditional COP measures in individuals with CAI (Hertel & Olmsted-Kramer, 2007; McKeon and Hertel, 2008a, McKeon and Hertel, 2008b; Wikstrom et al., 2010b) warrants the use of a spatiotemporal analysis such as TTB to quantify postural control during functional exercises. Examining COP excursions during the Lateral Step-Down Test, a relevant clinical assessment that has received little attention in the CAI literature (Grindstaff et al., 2017), would advance our understanding of the underlying mechanisms associated with poor postural control during unilateral weight-bearing exercises in individuals with CAI. Therefore, the purpose of this study was to assess traditional COP and TTB measures of postural control during a Lateral Step-Down Test in individuals with and without self-reported unilateral CAI. We hypothesized that individuals with CAI would demonstrate deficits in COP and TTB measures of postural control during the Lateral Step-Down Test in comparison to healthy controls.