POST-CONCUSSIVE CHANGES IN BALANCE AND POSTURAL STABILITY MEASURED WITH CANESENSE™ AND THE BALANCE ERROR SCORING SYSTEM (BESS) IN DIVISION I COLLEGIATE FOOTBALL PLAYERS: A CASE SERIES

Abstract

Introduction

Impairments in postural stability have been identified following sports-related concussion. CaneSense™ is a recently developed mobile lower limb motion capture system and mobile application for movement assessment which provides an objective measure of postural stability. One of the components within CaneSense™ is the Post-Concussive Excursion Index (PCEI), a measure of postural stability expressed as a percentage of symmetry between lower limbs.

Purpose

The purpose of this case series is to examine pre- and post-concussion differences using two separate measures, CaneSense™, and a known test, the Balance Error Scoring System (BESS), in Division I collegiate football players.

Methods

A convenience sample of eight football players diagnosed with a concussion, were the subjects in this case series. All subjects underwent baseline testing prior to the start of pre-season camp consisting of the single limb stance (SLS) test with CaneSense™ and the BESS test. Twenty-four to 72 hours following their concussion, SLS with CaneSense™ test and the BESS test, were administered. Segmental excursions for the thigh and shank segments for each lower limb were combined into the Post-Concussion Excursion Profile (PCEP), which represents each segment's maximum excursion in the medial-lateral and anterior-posterior direction. The PCEI is a single metric generated to quantify differences within subjects by comparing the PCEP value between lower limbs during SLS where 100% suggests absolute symmetry.

Results

The PCEI value decreased significantly post-concussion (41.43 ± 15.53% vs. 87.41 ± 6.05%, p < 0.001) demonstrating a 52.6% decrease in inter-limb symmetry when compared to baseline values. There was an unanticipated 36.36% improvement in composite BESS performance post-concussion (10.5 ± 4.87 errors vs. 16.5 ± 8.49 errors, p = 0.10).

Conclusions

Differences in inter-limb postural stability were found in subjects post-concussion. By assessing postural stability in both lower limbs individually, using the PCEI, impairments were detected that otherwise would have likely gone undiagnosed using the BESS test alone.

Levels of Evidence

Therapy, Level 4

INTRODUCTION

Management of sport-related concussions have become a serious concern in recent years because of the substantial increase in awareness of, education regarding, and reported incidence of concussion.^1,2 Concussions are often considered a transient injury and monitoring recovery by using appropriate clinical assessments, prescribing treatment, and determining clearance for return to sport is challenging, as overt impairments may resolve in a relatively short timeframe (7-10 days).^3–5,6–11 Short-term sequelae of concussions include functional disturbances and axonal injuries rather than grossly detectable structural brain damage and may present with a wide range of clinical signs and symptoms.^2-9,11-15

Despite the transient nature of concussion, cortical and postural impairments can be present for a significant period of time before returning to baseline.² In part, neuropathological evaluations have shown that concussion-induced axonopathy may persist for years.² Moreover, researchers have identified intracortical facilitation, motor-evoked potential (MEP) amplitude, and maximal voluntary muscle contractions to be negatively affected in the post-concussed population.^16-20 Increased MEP latencies and the associated decreased amplitude post-concussion suggest that the brain may be unable to effectively coordinate movement, which may be associated with impaired postural stability, increased reaction times, and the risk of acute lower extremity musculoskeletal (MSK) injury.²⁰

Impairments in postural control, postural stability, and neural activation patterns have been identified from months to years’ post-concussion despite apparent clinical recovery.^21-28 Concussions produce greater changes in balance and postural stability than has been previously believed.^14,20,29-44 Postural control under static conditions is typically referred to as “postural steadiness,” whereas the dynamic postural response to applied or volitional perturbations is called “postural stability”.⁴⁵ Postural stability is defined as the ability to maintain the position of the body, and specifically, the center of mass, within specific boundaries of space, referred to as stability limits.⁴⁶ Postural stability has been described as an essential component in assessing the efficacy of balance interventions.^47-49

The assessment of postural stability can provide an indirect means of identifying concussion-related neurophysiological abnormality.^27,50 The central nervous system (CNS) combines information from three pathways (i.e., visual, vestibular, and somatosensory systems) to maintain postural stability.⁵¹ The resultant efferent motor output that maintains postural stability travels down the descending tracts of the spinal cord and can either progress ipsilateral or contralateral (decussation) from the site of origin.⁵² Therefore, clinical presentation may produce bilateral, unilateral, or contralateral impairments to the potential site(s) of the injury(s).

Disrupted cortical pathways alter neural activation patterns resulting in impairments to postural stability, potentially explaining the increased risk of acute lower limb MSK injury post-concussion.^{16-20,27,33,41-42,53-59} The disruption in neural activation patterns can present as the inability to integrate and/or process sensory information quickly (slower reaction times) and/or efficiently between the visual, vestibular, and somatosensory systems.^{33,41,42,55-59} Disintegrations of the cortical pathways to the MSK system, have the potential to impair movement when performing high-level mobility skills.^20,27,53,54

The assessment of impaired postural stability has been performed during static and dynamic movement tasks.^36,39 Postural stability tests include a combination of single-limb stance (SLS) or double-limb stance, alterations in base of support, stressing of sensory system(s), use of different equipment and surfaces, and inclusion of dual-task conditions, such as level walking while undergoing a cognitive distractor task.^{29,34,35,38-40} Optimal timeframes for initial and repeated postural stability assessments is also unclear, as impairments post-concussion can linger beyond return to play.³⁷

Two common clinical tests for assessing postural stability post-concussion are the Balance Error Scoring System (BESS) and a dynamic posturography test known as the Sensory Organization Test (SOT).^6,55-58The BESS consists of three different stance positions on non-compliant and compliant surfaces: double-limb stance with narrow base of support, non-dominant limb SLS, and tandem stance with non-dominant foot as the posterior limb.^27,28,57,59 Recent literature suggests the use of the modified BESS (mBESS) for post-concussion testing.^56,58 The SOT objectively identifies postural control by assessing integration and weighting of visual, vestibular, and proprioceptive information during a specific task.^{27,29,57,60-62} Yet, Cavanaugh et al.²⁹ has suggested that SOT equilibrium scores may not be capable of detecting subtle changes in postural control. Not all clinics are able to administer the SOT because of the time to administer testing, clinical space restraints, advanced training requirements, and potentially cost-prohibitive equipment (NeuroCom^® Balance Master Equitest^® or NeuroCom^® Smart Equitest^® [NeuroCom International, Inc., Clackamas, OR]).

The emergence of mobile health (mHealth) and the use of wearable sensor technology have increased in popularity across healthcare disciplines because of the potential to reduce the limitations traditionally associated with performance testing and sports medicine. The use of inertial measurement unit (IMU) sensors provides clinicians with the ability to use instrumented, objective measures that are reproducible in a variety of sports-related environments or in combination with performance-based assessment measures. This case series used CaneSense™ (University of Miami, Department of Physical Therapy, Coral Gables, FL, USA), a mobile wireless sensor system and application for assessing human movement consisting of four IMUs secured in two elastic knee sleeves which communicates via Bluetooth low energy (BLE) to a mobile tablet. The IMU sensors were custom made at the University of Miami Functional Outcomes Research Evaluation Center and validated for estimating human kinematics against the gold-standard optical motion capture systems.^63-66

Demographic information including injury history and lower-limb kinematics during testing were obtained and analyzed via an iPad Air 2^® (Apple^®, Cupertino, USA) for all enrolled subjects using the CaneSense™ mobile app. The mobile app provides cues for the verbal instructions, and an instructive drawing to guide the progression of the testing. CaneSense™ IMU sensors are quick to don ( < 30 sec) and testing is also quick ( < 2 min). A component of CaneSense™ is the Post-Concussive Excursion Index (PCEI), a measure of postural stability expressed as a percentage of symmetry between lower limbs. A decrease in PCEI post-concussion is indicative of altered postural stability and greater asymmetry.

The purpose of this case series is to examine pre- and post-concussion differences using two separate measures, CaneSense™, and a known test, the Balance Error Scoring System (BESS), in Division I collegiate football players.

CASE DESCRIPTIONS

A convenience sample of eight Division I collegiate football players diagnosed with an in-season concussion was included in this case series. Prior to the start of fall football practice, the whole team completed the informed consent process and were baseline tested. At the time of pre-season testing, subjects were informed that their baseline data and any subsequent post-injury testing results for their cases could be potentially submitted for publication. The subjects’ confidentiality was protected according to the U.S. Health Insurance Portability and Accountability Act (HIPPA) and IRB approval for this case series was granted. The inclusion criteria for subjects was an in-season concussion diagnoses. Subjects were excluded from the case series if they were unable to follow commands post-concussion.

Baseline Testing

The subjects performed baseline testing solely with the tester in a quiet, well-lit indoor gymnasium. Baseline testing of postural stability consisted of the SLS test with CaneSense™ and the BESS test, respectively. Prior to pre-season testing, all the subjects reported to be right foot dominant as per the BESS testing script, therefore SLS testing during the BESS was performed with the left lower limb. During tandem standing, the left lower limb was positioned posteriorly.

History

The eight subjects who were enrolled in this case series sustained a concussion during either a practice or game. Once diagnosed with a concussion, none of the subjects were allowed to return to play as a safety precaution and were immediately placed in the University's concussion protocol which includes neurocognitive testing, neurological status assessment, and symptom severity measurement. The on-site clinician(s) noted that none of the subjects demonstrated signs indicative of gross motor impairment (e.g., step, stumble, fall, loss of coordination), nor alterations in mental status (e.g., dazed, stunned, confused) at the time of injury or during testing. Additionally, none of the subjects were taken to the hospital nor underwent any diagnostic imaging following the concussion. Table 1 provides a description of mechanism of injury and post-concussion clinical presentation for each subject.

Table 1.

Concussion Injury Description and Post-Concussion Clinical Presentation

Subjects	1	2	3	4	5	6	7	8
Mechanism of Injury	Tackled	Collision	Collision	Tackled	Collision	Collision	Collision	Tackled
Collision Location	Helmet	Helmet	Body	Helmet	Helmet	Body	Helmet	Helmet
Impact of Location of Collision	Left	Right	Right	Left	Front	Right	Left	Left
Delayed Onset of Symptoms	No	No	No	No	Yes	Yes	No	No
Alteration in Mental Status	Yes	No	Yes	Yes	Yes	Yes	No	No
Retrograde Amnesia	No	No	No	No	No	No	No	No
Post-traumatic Amnesia	No	No	No	No	No	Yes	No	No
Motor Impairment Present After Collision	No	No	Yes	No	No	No	No	No

POST-CONCUSSIVE ASSESSMMENT

Twenty-four to 72 hours following the diagnosis of concussion by the team physician, the subjects performed the CaneSense™ and BESS test in the same testing environment used during baseline testing. All subjects were symptomatic at the time of testing, however, were able to complete all static postural stability testing and were able to stand on each lower limb for 30 seconds. Dynamic postural stability tests in the early phase of recovery post-concussion were not included, as the authors recognize that the neurophysiologic demand for more complex movements should be assessed once the static elements of balance meet the threshold of time described above.

Single Limb Stance

The SLS test is often used as a measure of static postural stability and a threshold test for determining readiness to begin high-level exercise programs, such as plyometrics. The ability to maintain SLS can be used to detect differences between lower limbs and assist clinicians to determine if impairment is present.^62,64,67,68 Standing with arms crossed over their chest, subjects were asked to raise one foot over a 15cm cone placed on the floor directly in front of that foot. The stopwatch started when the foot was lifted off the floor and stopped when the foot returned to the floor, the foot fell below the cone, they hopped, arms became uncrossed, or 30 second(s) was achieved. A maximum of two trials were permitted for each lower limb to successfully achieved 30s. Subjects were given a 30s rest period between each trial.⁶⁹ Testers used the App to record all IMU data for the PCEI and SLS times to the nearest 0.02s.

Post-Concussive Excursion Index (PCEI)

To quantitatively assess postural stability, the CaneSense™ system generates a metric called Region of Limb Stability (ROLS).⁶⁴ Lower limb stability is defined by both thigh and shank movements of the supporting limb during SLS. Specifically, ROLS quantifies the area of excursion of the thigh and shank using acceleration data from the two IMUs imbedded in the elastic sleeve worn over the knee joint.⁶⁴

The segmental excursions for the thigh and shank segments for each lower limb can be seen in Figure 1a. The combination of the thigh and shank segment excursions are combined into the Post-Concussion Excursion Profile (PCEP) to provide a value. (Figure 1b) The PCEP value represents each segment's range of excursion in the medial-lateral and anterior-posterior direction. The PCEI is a single metric generated to quantify differences within subjects by comparing the PCEP value between lower limbs during SLS, whereby 100% suggests absolute symmetry. PCEI values ≤ 80% were considered to be a significant imbalance.⁷⁰ The lower limb with the greater PCEP values and values > 10 cm² indicated a postural stability impairment.

Figure 1.

An example of the segmental excursions for the thigh and shank segments for each lower limb. 1a) the combined the Post-Concussion Excursion Profile (PCEP) diagram. 1b) one numerical PCEP value area of the blue square in Figure 1b, which represents each segment's maximum excursion in the medial-lateral (ML) and anterior-posterior (AP) direction.

Concurrent validity has been established for the CaneSense™ ROLS values in assessing for area of excursion of the lower limbs.⁶⁴ Kim et al⁶⁴ compared excursion using the CaneSense™ to a three-dimensional optical motion analysis system (Vicon Motion Systems Ltd., UK) in a group of healthy adults.⁶⁴ There were high correlations (0.82-0.93) and no significant difference (p?>?0.05) in the tested parameters between the optical- and IMU-based systems.⁶⁴

Balance Error Scoring System

The three BESS stances were performed consecutively on a non-compliant firm surface and on a compliant medium-density foam square (Airex^®, Sins, Switzerland; 50 cm × 41 cm × 6 cm thick). The subjects were asked to close their eyes while holding these stance positions. The tester counted the number of errors the individual demonstrated during each 20s trial. Each error was considered a measure of postural instability. An error was defined as opening eyes, lifting hands off hips, stepping, stumbling or falling out of position, lifting forefoot or heel, abducting the hip by more than 30 °, or failing to return to the test position > 5s. Scores were determined by calculating the number of errors committed during each of the 20s trials, with an absolute 5s maintenance of balance required for testing. Each error counted as one point and the total score was the sum of all the errors, with the best performance being a score of 0 errors.^27,59 Ten errors is the maximum number allowed per trial. BESS composite scores were calculated and used for analysis.

Statistical Analysis

Statistical analysis was performed using IBM^® SPSS version 22. Descriptive statistics were used to characterize pre-post-concussion CaneSense™ and BESS composite scores. Paired samples t-test was used to examine the pre-post-concussion differences in PCEI and BESS composite scores. Significance was set at p ≤ 0.05. Effect sizes were calculated for change in PCEP, PCEI, Left SLS No Foam BESS (NFBE), Left SLS Foam BESS (FBE), and Composite BESS Errors (CBE) post-concussion.

OUTCOMES

The mean, standard deviation (SD) and range for pre-season baseline and post-concussion PCEP, PCEI, and BESS values are described in (Table 2) for the eight subjects. Pre-season baseline dominant and non-dominant PCEP (5.13 ± 1.71 cm² and 5.92 ± 1.64 cm²) and PCEI values (87.41 ± 6.05%) are consistent with pre-season baseline values on healthy non-injured athletes PCEP (6.70 ± 3.47 cm² and 6.03 ± 3.30 cm²) and PCEI (89.7 ± 6.03%).⁷¹ Pre-season BESS composite scores are consistent with published ranges for subjects collected at pre-season.⁷² Post-concussion changes in PCEP values for the dominant (13.05 ± 13.87 cm², 154.39% increase) and non-dominant (9.73 ± 8.21 cm², 64.36% increase) limbs were found. However, changes in PCEP for the dominant (p = 0.14) and non-dominant limb (p = 0.23) were not statistically significantly different. The PCEI value decreased significantly post-concussion (41.43 ± 15.53% vs. 87.41 ± 6.05%, p < 0.001) demonstrating a 52.6% decrease when compared to pre-season baseline values. The effect sizes for concussion on PCEP for the dominant and non-dominant limb (4.63 and 2.32) and PCEI (-7.07) were all considered very large. The effect sizes of concussion on left SLS NFBE (-0.58), left SLS FBE (-0.72), and CBE (-0.71) were moderate. Interestingly, BESS left SLS performance not on foam (p = 0.11), on foam (p = 0.17), and BESS composite scores (p = 0.10) had generally lower error scores post-concussion, however, they did not reach statistically significant differences.

Table 2.

Differences in baseline and post-concussion values of the Post-Concussive Excursion Index (PCEI) and composite Balance Error Scoring System (BESS) errors

	Pre-season Baseline	Post-concussion	Mean Change	Effect Size	95% Confidence Interval	Difference Between Testing (p-value)
Mean ± SD (range)	Mean ± SD (range)
DL PCEP (cm2)	5.13 ± 1.71 (2.71 – 7.65)	13.05 ± 13.87 (3.62 – 42.21)	-7.92	4.63	-19.15 – 3.31	0.14
NDL PCEP (cm2)	5.92 ± 1.64 (3.26 – 8.14)	9.73 ± 8.21 (1.08 – 23.12)	-3.81	2.32	-10.61 – 2.98	0.23
PCEI (%)	87.41 ± 6.05 (79.01 – 97.75)	41.43 ± 15.53 (20.25 – 68.78)	45.98	-7.07	30.95 – 61.02	<0.001
Left SLS NFBE (n)	3.63 ± 3.16 (0 – 8)	1.88 ± 1.25 (0 – 4)	1.75	-0.58	-0.52 – 4.02	0.11
Left SLS FBE (n)	6.00 ± 3.42 (2 – 10)	3.63 ± 2.77 (0 – 8)	2.38	-0.72	-1.31 – 6.06	0.17
CBE (n)	16.50 ± 8.49 (4 – 29)	10.50 ± 4.87 (2 – 17)	6.00	-0.71	-1.46 – 13.46	0.10

BOLD = Statistically significant value (p<0.05); DL PCEP = Dominant Limb Post-Concussion Excursion Profile; NDL PCEP = Non-Dominant Limb Post-Concussion Profile; PCEI = Post Concussive Excursion Index; Left SLS NFBE = Left Single Limb Stance No Foam BESS test; Left SLS FBE = Left Single Limb Stance Foam BESS Test; CBE = Composite BESS Errors

Table 3 presents the changes in PCEP, PCEI, and BESS values for each subject. Interestingly, a trend was found in that the PCEP values for one lower limb remained the same while the other limb was worse than baseline values. Specifically, change in dominant limb PCEP values ranged from 5% – 794% and change in non-dominant limb PCEP values ranged from 12% – 306%, respectively. The PCEI post-concussion were all under 75%, with a range from 14.48% – 74.37%, indicating there to be a significant imbalance. Figure 2 graphically depicts ROLS segmental excursion and PCEP as an example (from Subject 1) of the left lower limb or non-dominant ROLS and PCEP values. The pre- and post-concussion values are similar, with an increase in excursion of 4 cm and a change of 60%. Figure 3 graphically depicts ROLS segmental excursion and PCEP as an example (from Subject 1) of the right lower limb or dominant ROLS and PCEP values. The pre- and post-concussion values were different with an increase of 35 cm and a change of 452%.

Table 3.

Pre-season baseline and Post-Concussion Excursion Index values and Balance Error Scoring System errors

Sub	1			2			3			4			5			6			7			8
OM	Pre	Post	%	Pre	Post	%	Pre	Post	%	Pre	Post	%	Pre	Post	%	Pre	Post	%	Pre	Post	%	Pre	Post	%
DL PCEP (cm2)	7.65	42.21	451.77	5.47	15.28	179.34	4.63	3.62	21.81	3.41	4.47	22.37	7.16	4.18	41.62	4.34	4.13	5.49	2.71	24.23	794.10	5.46	6.30	11.70
NDL PCEP (cm2)	6.82	10.9	59.82	8.14	8.01	12.09	5.69	23.12	306.33	3.26	1.08	66.87	5.71	19.80	246.76	6.02	10.46	73.75	4.15	2.73	34.22	7.58	1.77	76.65
PCEI (%)	94.26	41.05	56.45	80.38	68.67	14.48	89.73	27.08	69.82	97.75	38.92	60.18	88.73	34.86	60.71	84.12	56.61	32.70	79.01	20.25	74.37	85.33	43.87	48.59
Left SLS NFBE (n)	0	0	0	8	2	75	5	3	40	1	1	0	4	4	0	8	2	75	1	1	0	2	2	0
Left SLS FBE (n)	10	0	100	9	2	77.78	10	5	50	2	3	50	6	8	-33.33	6	7	16.67	2	2	0	3	2	33.33
CBE (n)	19	2	89	23	7	70.00	21	11	47.62	4	8	100	18	14	22.22	29	17	41.38	7	10	42.86	11	15	36.36

BOLD = percentage values that are negative; Sub = Subjects; OM = Outcome Measures; DL = Dominant limb, NDL = Non-dominant limb, NFBE = No foam BESS errors, FBE = Foam BESS errors, CBE = Cumulative BESS errors, % = Percent change between pre-season baseline and post-concussion outcome results.

* DS: Dominant side, NDS: Non-dominant side, NFBE: No foam BESS errors, FBE: Foam BESS errors, CBE: Cumulative BESS errors.

Figure 2.

A graphical depiction of an example (Subject 1) Region of Limb Stability (ROLS) segmental excursion and Post-Concussion Excursion Profile (PCEP) for the left lower limb (non-dominant) displayed as ROLS and PCEP values. The pre- and post-concussion values are similar, with an increase in excursion of 4 cm and a change of 60%.

Figure 3.

A graphical depiction of an example (Subject 1) Region of Limb Stability (ROLS) segmental excursion and Post-Concussion Excursion Profile (PCEP) for the right lower limb (dominant) displayed as ROLS and PCEP values. The pre- and post-concussion values were very different with an increase of 35 cm and a change of 452%.

DISCUSSION

Assessment of postural stability post-concussion appears to be a valuable tool for screening and has the potential to guide clinical decision making.^27,51,53,56 The results of this case series suggest that testing SLS with both lower limbs using the CaneSense™ to assess changes in postural stability in subjects after sustaining a concussion may be an effective measure to quantify the extent of injury. Although the p-values demonstrated no difference between baseline and post-concussion PCEP values, the effect size of concussion on postural stability values as measured by the CaneSense™ of the dominant and non-dominant limb were very large. In addition, when examining the symmetry of postural stability between both limbs (PCEI), the effect size was even greater, suggesting that lower limb excursion was an effective method of assessing change in postural stability post-concussion.

The ability to perform complex movements depends upon the activation of networks of neurons in the motor cortex and brainstem.^2,52 Motor areas of the cerebral cortex direct purposeful, voluntary movement, while neurons located in brainstem nuclei direct automatic movements such as postural control that are both ipsilateral and contralateral.^2,52 Consequently, injuries to the motor cortex and brainstem can present with disruptions in movement and alterations of balance strategies.^2,52 When considering the neuroanatomy of the CNS and the potential variations in motor and sensory impairments that may present clinically, testing of both lower limbs should be strongly considered. Therefore, using ROLS and PCEP to assess postural stability for each lower limb may be beneficial.

Improvements were noted in post-concussion BESS test performance in this case series Five of the eight subjects demonstrated better BESS scores post-concussion, with a mean improvement of 11.8 points which could be attributed to problems with the assessment. The remaining three subjects had higher BESS composite scores, with a mean improvement of 3.67 points. The BESS test has several limitations which include low inter and intrarater reliability, heavy reliability on rater interpretation of errors, practice and learning effect, and setting differences during testing (training room vs. sideline during a competition).^53,56,73-77 The BESS has also been reported to have a low sensitivity statistic (0.34) and an inability to detect balance dysfunction seven days after initial concussion.⁵³

Researchers have identified a potential risk of MSK injury post-concussion that extends beyond the acute stage of injury.^{6,13,14,20,21,23,36,37,43,44,59,78-85} Two factors that may contribute to the increased risk include undetected impairments and decreased postural stability. Through the use of ROLS PCEI results, clinicians could prescribe a more targeted rehabilitation program based on the identification of specific deficits. Postural stability requires numerous resources for balance and postural control including: biomechanical constraints, sensory strategies, dynamic controls, orientation to space, movement strategies, and cognitive processing.⁸⁶ Each of these resources has several components that can be addressed with rehabilitation but must be properly identified before the appropriate treatment may be prescribed. Moreover, impairments to balance and postural control, especially in previously concussed athletes, may contribute to the risk of subsequent lower limb MSK injury.^{14,15,20,44,83,84}

ROLS, PCEP, and PCEI values can help to provide insight into impairment of postural stability. The clinical benefits of ROLS, PCEP, and PCEI versus BESS includes: 1) assessment of symmetry in SLS for both limbs, 2) objective numeric comparison of limb excursion with respect to area and direction, 3) identification of impairments in postural stability in multiple planes, 4) objective measure of change over time, 5) potential for targeted treatment prescription, and 6) immediate, objective performance feedback.

The present study involved several limitations that should be considered in future works. First, the population was small, only eight subjects, which may prohibit extrapolating these findings to the general population. Next, considerations on expanding the use of PCEP bilateral assessments of postural stability with a greater number of athletes, across ages and genders, type of sport playing when injured, and accounting for past medical history. Likewise, the ability to use repeated measures to longitudinally track change over time may prove useful in establishing post-concussive return to play criteria. Continued use of the PCEP and PCEI will assist sports medicine clinicians to accurately determine sensorimotor and postural control deficits that may have otherwise gone unrecognized.

CONCLUSIONS

The results of this case series indicate that significant differences in lower limb postural stability were found post-concussion as measured by the CaneSense™. The PCEP and PCEI afford reproducible data that can determine differences between lower limbs and document changes over time in postural stability. Of note, the BESS test was unable to identify dominant limb postural stability deficits with these subjects. The use of mobile, wireless technologies provides a practical form of objective testing for concussion injuries. The use of CaneSense™ with the PCEP and PCEI metrics provides sports medicine clinicians with an objective measure of postural stability for both lower limbs that can be administered in a variety of environments. Future work will be required to determine the utility of the PCEP and PCEI with respect to assessment of athletes who sustain a concussion and return to sport criteria.