Relationships between jumping performance, activity level and perceived joint status in subjects with and without chronic ankle instability

CLAUDIO LEGNANI1, MATTEO SALADINI2, MARTINA FARALDI3, BEATRICE ANSELMI2, GIUSEPPE M. PERETTI4,5, ENRICO BORGO1, ALBERTO VENTURA1

1IRCCS Istituto Ortopedico Galeazzi, Sports Traumatology and Minimally Invasive Articular Surgery Center, Milan, Italy; 2University of Milan, Italy; 3IRCCS Istituto Ortopedico Galeazzi, Laboratory of Experimental Biochemistry and Advanced Diagnostics, Milan, Italy; 4IRCCS Istituto Ortopedico Galeazzi, EUORR Unit, Milan, Italy; 5Department of Biomedical Sciences for Health, University of Milan, Italy.

Summary. Background. Chronic ankle instability (CAI) could be a common consequence of one or multiple ankle sprains and may lead to long-term functional impairments. In literature, most studies have investigated these impairments using only a single functional task, while few have employed a comprehensive battery of tests. The purpose of this study was to detect correlations between functional ability, activity level and perceived ankle status to find out differences between patients affected by CAI and healthy subjects using a jump test battery. Methods. 42 subjects ranging in age from 18 to 45 were included in the present study. A group of 21 patients with CAI was matched for number age, sex, and body mass index to a control group of healthy volunteers with no history of lower limb pathology. The American Orthopaedic Foot & Ankle Society ankle-hindfoot scale (AOFAS), and Tegner activity level were determined for all subjects. An OptoGait (Microgate, Bolzano, Italy) infrared sensor device was used to measure jumping performance. The test battery included countermovement jumps (CMJs), drop jumps (DJs), side-hop tests. Results. A significant difference (lower in CAI patients) in both AOFAS and Tegner scores between healthy individuals and CAI patients (p<0.001 and p<0.01, respectively) was observed and weak to moderate positive correlation was found for both CMJ and DJ and point scales in CAI patients (p<0.01). Conclusions. In healthy individuals, jumping performance appears to depend on overall physical activity, whereas in CAI patients it is more closely associated with both perceived ankle function and objective impairments. Our findings support the recommendation to combine patient-reported outcomes and functional performance tests in the clinical assessment and management of CAI.

Key words. Ankle, chronic ankle instability, vertical jump, battery test.

Relazioni tra performance nei salti, livello di attività e percezione dello stato articolare in soggetti con e senza instabilità cronica di caviglia

Riassunto. Introduzione. L’instabilità cronica di caviglia (CAI, Chronic Ankle Instability) può rappresentare una conseguenza comune di una o più distorsioni di caviglia e può portare a deficit funzionali a lungo termine. In letteratura, la maggior parte degli studi ha indagato tali deficit utilizzando un singolo test funzionale, mentre pochi studi hanno adoperato una batteria completa di test. Scopo di questo studio è stato rilevare le correlazioni esistenti tra la capacità funzionale, il livello di attività e la percezione dello stato della caviglia, al fine di individuare eventuali differenze tra pazienti affetti da CAI e soggetti sani mediante una batteria di test di salto. Metodi. Sono stati inclusi nello studio 42 soggetti di età compresa tra 18 e 45 anni. Un gruppo di 21 pazienti con CAI è stato abbinato per età, sesso e indice di massa corporea a un gruppo di controllo di volontari sani senza storia di patologie agli arti inferiori. Per tutti i soggetti sono stati determinati il punteggio dell’American Orthopaedic Foot & Ankle Society (AOFAS) e il livello di attività secondo la scala di Tegner. Le prestazioni nei salti sono state misurate con un sistema a sensori a infrarossi OptoGait (Microgate, Bolzano, Italia). La batteria di test comprendeva countermovement jumps (CMJ), drop jumps (DJ) e side-hop test. Risultati. È stata osservata una differenza significativa (inferiore nei pazienti con CAI) nei punteggi AOFAS e Tegner tra soggetti sani e pazienti con CAI (p<0,001 e p<0,01, rispettivamente). Nei pazienti con CAI è stata inoltre riscontrata una correlazione positiva da debole a moderata tra i CMJ e DJ e i punteggi delle scale di valutazione (p<0,01). Conclusioni. Nei soggetti sani, le prestazioni nei salti sembrano dipendere dal livello generale di attività fisica, mentre nei pazienti con CAI risultano più strettamente associate sia alla percezione della funzionalità della caviglia sia ai deficit oggettivamente rilevabili della stessa. I nostri risultati supportano la raccomandazione di combinare le valutazioni fornite dai pazienti con i test di performance funzionale, integrando il tutto nella valutazione clinica e nella gestione della CAI.

Parole chiave. Caviglia, instabilità cronica di caviglia, salto verticale, batteria di test.

Introduction

Chronic ankle instability (CAI) is a perceived joint impairment that can usually follow one or multiple ankle sprains1. It has been reported that approximately 40% of individuals who have sustained an ankle sprain subsequently develop chronic ankle instability2. Prior research has shown that, in comparison to healthy individuals, patients with CAI have decreased power and balance control, potentially leading to proprioceptive deficits adversely affecting postural stability and gait3. Functional and structural brain adaptations have also been identified in those patients. These neural changes correlate with poorer self-reported function and clinical outcomes4.

There is evidence that jump tests, which assess explosive strength, coordination, and knee extensor strength, can be used to examine lower limb biomechanics5,6. These tests have already been used to facilitate the assessment of patients with pathologic knee disorders, such as those following anterior cruciate ligament reconstruction7. Thus, impairments in neuromuscular function during activities involving jumping and landing may be an indication of a dysfunctional joint-protecting control system8. However, the majority of studies only employed one functional task to evaluate dynamic postural control, although in order to assess functional capacity, multiple tests should be utilized to analyze joint kinematics5. Therefore, a battery of jump tests may investigate more accurately and consistently information regarding the distinctions between CAI patients and healthy participants.

There hasn’t been much research done on the biomechanics of jump-landing and bipodalic and monopodalic vertical jump activities in CAI patients. Neuromuscular changes have been demonstrated both during walking and when doing strength and balance tests9-11.

Jump battery tests are widely used in research, but their use in the clinical setting is limited, and their capacity to identify impairments associated with disease remains controversial.

In addition, the evaluation of subjective confidence is frequently employed to assess patient ability to cope with CAI. A relationship between patient reported outcomes and functional performance tests in subjects with a history of ankle sprain has been previously reported12. This study sought to see whether relationships between perceived ankle state, activity level, and jumping performance might exist. The hypotheses were that that jumping performance correlates to subjective and functional ratings and that patients with CAI would demonstrate lower activity level and lower perceived ankle status. Findings from this study may support the development of more targeted rehabilitation strategies and goals for CAI patients.

Materials and methods

Patients’ recruitment

In this study, 42 subjects between the ages of 18 and 45 were included, as previously detailed in a parent study13. The research group consisted of 21 CAI-affected patients who were matched to a control group of 21 healthy volunteers in terms of age, male to female ratio, and BMI. This study was authorized by the Ethics Committee of IRCCS San Raffaele Hospital in Milan, Italy (IRB number: 177/INT/2022). Informed permission was signed by each patient.

Ages 18 to 45, BMI ≤30, and no neurological conditions preventing the ability to conduct a jumping testing were the inclusion criteria. Patients who refused to sign the consent form, had prior ligamental ankle surgery (including on the contralateral side), or, in case of female patients, were pregnant at the time of examination were all excluded.

Patients’ assessment

• All patients completed the American Orthopaedic Foot and Ankle Society (AOFAS) ankle and hindfoot questionnaire, which incorporates items about pain (40 points), function (50 points), and alignment (10 points). At the end a score from 0 to 100 is given: higher scores indicate better ankle and hindfoot status14.

• Activity level was assesed using the Tegner Scale, a patient-reported outcome measure which scores subjects from 0 to 10 points on the basis of their activity level. Level 0 indicates disability due to injury, levels 1 to 3 daily activities, levels 4 to 6 recreational sports, levels 7 to 10 show competitive sports15.

A series of vertical jump tests were performed using an infrared optical acquisition system (OptoGait; Microgate, Bolzano, Italy), in accordance to a previous protocol16. Patients were told to warm up with practice trials for ten minutes. The tests included the monopodalic countermovement jump (CMJ), drop jump (DJ), and side hop test, which was conducted with the uninjured (CAI group) and dominant (control group) limb first, followed by the injured/non dominant limb. Every functional test was run three times. There was a designated period of rest in between each jumping performance. Test results were measured in terms of flight duration (milliseconds) and distance (centimeters), and the average of all completed trials was used to compute the score.

Statistical analysis

Data were analyzed using Graphpad Prism v8.0 (Prism Software, La Jolla, CA, USA). Categorical variables were reported as absolute and relative frequencies for each group, and comparisons were performed using Fisher’s exact test or Chi-square test. After verifying the normal distribution of the continuous variables using the Shapiro-Wilk test, these were compared between the two groups using the Student test for unpaired data or, in case of non-normal distribution, the Mann-Whitney test or multiple comparison with Holm-Sidack correction. Association analysis between patient characteristics and the analyzed variables has been performed by Spearman’s rank correlation. P values less than 0.05 were considered statistically significant.

G*power was performed to calculate sample size using mean and SD in the control group of 38.1±6.7 cm based on a previous study17. The power and the level of significance was set at 80% and 0.05 respectively. Hypothesizing a between-groups difference of 5 cm, 42 participants were required, 21 for each group.

Results

No statistically significant differences between the two groups were observed concerning age, sex, and body mass index (table 1).




A significant difference (lower in CAI patients) in both AOFAS and Tegner scores between healthy individuals and CAI patients (p<0.001 and p<0.01, respectively) was observed (figure 1). During monopodalic side-hop test, statistically significant increased performance was observed in healthy participants compared to CAI patients (p < 0.01, figure 2).







Correlation between jump battery tests and point scales

Correlation between CMJ, DJ and side-hop tests and point scales demonstrated moderate positive correlation with AOFAS scale (p<0.01, rs ranging from 0.57 and 0.74) in CAI patients.

Similarly, positive correlation was observed for jumping tests and Tegner activity level in the study group (p<0.05, rs ranging from 0.44 and 0.78).

A statistically significant moderate to strong correlation (rs ranging from 0.58 to 0.77) was reported between jump tests and Tegner scores in the control group (p<0.01).

Conversely, no statistically significant correlation was reported between jump tests and AOFAS scores in the control group (p=n.s.).

Results are reported in detail in table 2.




Discussion

According to our findings, patients with CAI reported lower AOFAS and Tegner scores compared to control group, reflecting reduced ankle function and activity levels.

Moderate correlations between vertical jump tests and functional ratings were reported in CAI patients, indicating that lower jumping performance is associated with poorer self-reported ankle function which suggests that neuromuscular impairments can affect both subjective and objective functional outcomes. Among healthy participants, Tegner activity levels correlated moderately to strongly with jumping performance, while no significant correlation was found between jump tests and AOFAS scores. This suggests that in healthy individuals, perceived ankle function may not directly limit or predict athletic performance, whereas in CAI patients, subjective impairments are closely linked to neuromuscular deficits.

Functional test batteries have been developed in addition to PROMs to assess deficits in individuals with CAI who wish to lead an active lifestyle, as CAI is linked to alterations in kinematic patterns during walking and athletic activities18.

Prior studies have demonstrated that the vertical jump is a reliable way to assess quadriceps explosive power, strength, and neuromuscular control in the lower limbs19-22. In order to determine the degree of impairment affecting patients with CAI, a series of vertical jump tests was employed in the current investigation to identify asymmetries between limbs and between patients with CAI and healthy volunteers.

Overall, our results show that higher levels of felt instability were linked to lower reported ankle function and higher reported impairment.

Our findings reflect those of Suttmiller et al.23 which imply that low reported ankle function during exercise is caused by pain, high levels of perceived instability, and fear associated to injuries, which may encourage activity avoidance behaviors. These avoidant behaviors over time may result in brain adaptations that encourage avoidance even more and cause the movement-behavior deficits common to people with CAI, including decreased levels of physical activity and abnormal movement patterns and poor balance.

It is generally known that CAI can lead to people reporting increased degrees of global impairment and deficiencies in joint function, while it is unclear how this relates to activity level and perceived ankle status. According to our research, higher levels of perceived ankle status and activity level correlated to higher jumping performance. Given that perceived instability is one of the hallmark symptoms of CAI, it is not unexpected that this variable would play a significant role in predicting athletic ability. This result is in line with that of Wikstrom et al.24, who found associations between function and reported pain in CAI patients.

The weakest correlation was reported between side-hop tests and Tegner score in patients affected by CAI. Therefore, interestingly, our results are consistent with the finding that monopodalic vertical jump and landing tests, rather than lateral side hop tests, are more beneficial in predicting the activity level of patients, thus giving an esteem on sporting ability.

Our study possesses limitations which should be acknowledged. First, its small sample size, which although a power analysis was conducted, could make difficult to identify minimal variations in some parameters across groups. OptoGait was selected because it is an inexpensive, user-friendly tool that can be practical in measuring functional ability and is easy to use in a clinical context. We recognize that a variety of factors affect jumping ability, and that using jumping capacity as a measure of neuromuscular function to look into ankle pathology is a further limitation warranting future research.

Conclusions

Patients with CAI reported lower AOFAS and Tegner scores compared to control group. Moderate correlations between vertical jump tests and functional ratings were reported in CAI patients. Tegner activity level correlated moderately to strongly to jumping ability in the control group, while no correlations were reported between jump tests and AOFAS scale among healthy volunteers.

These findings suggest that healthy individuals seem to have jumping performance which is more related to overall activity level than to specific ankle function; whereas neuromuscular impairments in CAI patients are reflected in both subjective assessments and objective performance measures. This highlights the potential utility of combining patient-reported outcomes with functional testing to gain a comprehensive understanding of ankle instability in order to optimize the treatment of CAI patients.

Conflicts of interest. The authors declare that there is no conflict of interest.

Funding. The research and APC were funded by the Italian Ministry of Health – Ricerca Corrente.

Authors’ contributions. CL, AV and GM Peretti have given substantial contributions to the conception or the design of the manuscript, MS, BA, MF and EB to acquisition, analysis and interpretation of the data. All authors have participated to drafting the manuscript, AV revised it critically. All authors read and approved the final version of the manuscript.

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