Study design Institutional Review Board approval:
We conducted a historical cohort study to evaluate the potential of the LESS-RT in predicting overuse injuries in general, and ankle sprains in particular among IDF combat soldiers. The predictive variable used in this study was LESS-RT score. Subjects were followed during a 12-month follow-up period beginning from the date of LESS-RT examination for two main outcome variables: 1.incidence of overuse injuries 2. Occurrence of ankle sprains.
This study was approved by the IDF’s Institutional Review Board (IRB), (Approval number: 1634-2015). Data analysis was performed using anonymized databases after exclusion of all identifying details.
Overuse injury Definition:
Overuse injuries were tallied if they satisfied all of the following criteria:
1. At least two identical musculoskeletal complaints during a consecutive period of 2 weeks.
2. At least one objective sign upon physical examination.
3. A significant reduction in function or physical performance due to the complaint.
It should be emphasized that the term overuse is referred to the mechanism of the injury (eg. Injury caused by repetitive stress which accumulates to a significant process of wear, resulting in severe tissue damage and insufficiency). This mechanism may be responsible not only for chronic injuries but also for acute injuries where tissues like muscles, tendons and ligaments may abruptly collapse during mild to moderate physical efforts resulting in complete or partial tears.
Ankle sprains were diagnosed by IDF physicians and certified orthopedic surgeons affiliated with the IDF.
Re-injury was defined as recurrence of a specific injury within the 12-month follow-up period and these were not tallied as an additional injury.
Subjects:
All IDF's soldiers are medically screened before recruitment and only those that are medically fit for combat service will be recruited to combat units. In 2014, the IDF first instituted its “Injury Prevention and Rehabilitation Center” (IPARC). The primary objective of this center was to evaluate combat soldiers prior to and during their enrollment in combat military units. The soldiers evaluated at IPARC hail from a variety of IDF combat units with varying activity levels including infantry training units and brigades, Special Forces, and commanders training units (Phase 2 training). The superior command of the Israeli field forces decided which of the units would be screened at IPARC, hence, The study's population is not necessarily representing the entire IDF’s combat soldier population. A total of 2,474 IDF soldiers assessed at IPARC within the first two years of its launch (2014-2016) were included in this study. Soldiers with any lower extremity injury (including overuse/ankle sprain) in the 3 months prior to performance of the LESS-RT examination or those with lower limb anatomical variations, (such as genu varus or valgus as documented by IDF physicians in the soldiers’ medical records), were excluded. During the screening process at IPARC, the soldiers undergo a battery of clinical movement screening tests including the LESS-RT.
The screening at IPARC predominantly occurred during the first 6 month of the soldiers' military service.
LESS-RT test procedure:
The subjects in this study performed the LESS-RT according to the method outlined by Padua et al.25 The three-step jump-landing task, which is identical to that of the original LESS, involves a forward jump from a 30-cm-high box onto a target landing zone and is followed by an immediate rebound jump to maximal vertical height. The landing area is situated at an approximate distance of half of the participant's height18,19. The LESS-RT uses 10 scoring items to identify gross movement errors25. These are scored in real-time and the cumulative result is used to assess potentially high-risk jump-landing biomechanics18-28. Half of the items are scored on a 2-point ordinal scale (0,1) and the other half on a 3-point ordinal scale (0, 1, and 2) (see table 1).
|
LESS-RT Item
|
Rater Perspective
|
Maximum Score
|
1
|
Stance width
|
Frontal
|
1
|
2
|
Maximum foot-rotation position
|
Frontal
|
1
|
3
|
Initial foot contact
|
Frontal
|
1
|
4
|
Maximum knee-valgus angle
|
Frontal
|
2
|
5
|
Amount of lateral trunk flexion
|
Frontal
|
1
|
6
|
Initial landing of feet
|
Sagittal
|
1
|
7
|
Amount of knee-flexion displacement
|
Sagittal
|
2
|
8
|
Amount of trunk-flexion displacement
|
Sagittal
|
2
|
9
|
Total joint displacement in the sagittal plane
|
Sagittal
|
2
|
10
|
Overall impression
|
Both
|
2
|
Table 1. Items Scored in the in the Landing Error Scoring System-Real Time (LESS-RT)
The cumulative score ranges from 0 to 15 with lower scores indicating fewer accumulated biomechanical errors. The jump-landing task is repeated four times in order to enable ample time and reiteration for scoring the test in concurrence with its performance. Tests were assessed by IDF physical therapists who gauged two repetitions from the frontal plane, and two from the sagittal plane as performed in the study by Padua et al.25 These scorers did not have previous experience in rating LESS or LESS-RT tests and the identity of the raters in each session was not recorded.
Data collection:
Soldiers’ demographic data and LESS-RT scores were acquired from IPARC’s computerized database. Data pertaining to medical history and incidence of overuse injuries and ankle sprains were collected from the IDF’s computerized medical record system – CPR® with a follow-up period of one year from LESS-RT performance.
For optimal identification of overuse injuries and ankle sprains, ICD-9 diagnostic codes were used as well as a novel text identification program that was developed by the IDF’s medical forces information branch. All data were anonymized and introduced into a Microsoft Office Excel® spreadsheet which served for further statistical analysis.
Statistical Analyses:
Statistical analysis was performed using SPSS® 23.0 (IBM SPSS Statistics, New York, USA). Descriptive statistics were calculated and displayed using means and standard deviations for continuous variables, median for scales, and frequencies for categorical variables. The chi-square test was used for the statistical significance when comparing two dichotomous variables.
Student’s t-test was used to determine the statistical significance when comparing quantitative variables divided into 2 categories such as injury outcomes. Shapiro Wilks test was used to evaluate whether variables were normally distributed. . Mann–Whitney U test was used in case variables were normally distribution. The analysis of variance test (ANOVA) was used to assess statistical significance when comparing categorical variables of more than 2 groups. Receiver operator characteristic (ROC) analyses were performed to evaluate the LESS-RT’s potential as a predictive tool for overuse injuries and ankle sprains and to potentially obtain optimal cut-off values for different risk categories.