Design
From Sep 2018 to Apr 2019, 20 CAI patients who were diagnosed as grade III ligament injury and ready for rehabilitation were included in the study. A priori power analysis was completed using data from a previous study in which the researchers examined the effects of a similar balance-training program12. The study was approved by the IRB Medical Committee of our hospital (IRB00006761-M2019164) and the written content was obtained from all patients. The study was registered in Chinese Clinical Trial Registry (ChiCTR), and the number was ChiCTR1900023999.
Patient enrollment
The inclusion criteria were (i) aging from 18 to 40, (ii) a history of at least one significant lateral ankle sprain (at least 12 months prior to study enrolment) that caused inflammatory symptoms and disrupted activity, (iii) the most recent ankle sprain occurred >3 months prior to study participation, (iv) reports of the previously injured joint “giving way” and/or recurrent sprain and/or “feelings of instability” (v) scoring <24 on the Cumberland Ankle Instability Tool (CAIT)13; grade III14-15 injury of anterior talofibular ligament (ATFL) and/or calcaneofibular ligament (CFL) confirmed by both MRI and positive anterior drawer test (increased translation of 3 mm compared to the uninjured side or an absolute value of 10 mm of displacement)16 and talar tilt test(10° of absolute talar tilt or 5° difference compared to the contralateral side)17 by TELOS SD 900 Stress Device (Austin & Associates, inc. USA). All patients presented without a history of neurological or orthopedic impairment. Patients with combined intra-articular lesions (OCLs, osteophyte, impingement, loose body, etc), a history of surgery, fracture requiring realignment and/or acute injury to the musculoskeletal structures (bone, joint structure and/or nerve) in either lower limb were excluded.
Upon enrollment, all the patients’ basic information was collected and evaluated, including the gender, age, height, weight, involved side, pre-duration, sprain time and the Beighton score. The Beighton score≥4 was defined as the generalized joint hypermobility (gJHM). Then all the participants underwent the 3-month balance training intervention. The progressive balance-training program divided into 24 supervised training sessions, two sessions (60 minutes each session) per week. The postintervention data-collection session occurred within 48 hours after the intervention ended. A follow-up session was performed 3 months, 6 months and 1 year since the pre-intervention data-collection session. Participants were instructed to cease all interventions during the follow-up session. During each data-collection session, we administered the patient-oriented outcomes (Foot and Ankle Ability Measure (FAAM), Cumberland Ankle Instability Tool (CAIT)) before evaluating the disease-oriented outcomes (isometric ankle strength, foot pressure and static and dynamic postural control).
Table 1. Participants’ information
Characteristics (n=20)
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Values
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Age, y
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26.4 ± 5.2
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Height, cm
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167.1± 8.4
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Weight, kg
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60.3 ±9.5
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No. of sprains
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8.2 ± 4.1
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Months since last sprain
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21.1 ± 21.6
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Sex, men: women
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12: 8
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Beighton score
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3.3 ± 2.3
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CAIT
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15.4±5.3
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FAAM ADL
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67.6±10.3
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FAAM sport
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55.9±11.4
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FAAM, Foot and Ankle Ability Measure, CAIT, Cumberland Ankle Instability Tool.
Plantar pressure and posture control evaluation
The patients underwent three trials of single-limb stance on each leg with eyes closed on a force plate (AMTI; Watertown, MA, USA) for 10s10, 18. COP data were calculated from the three-dimensional force and moment signals and sampled at a rate of 50 Hz. 18 Subjects were instructed to stand as still as possible during testing with arms folded across their chests, holding the opposite limb at approximately 45° of knee flexion and 30° of hip flexion in accordance. If a subject touched down the ground, contacted with the stance limb, or was unable to maintain standing posture during the 10-s trial, the trial was terminated and repeated. TTB measures and COP measures were computed separately in the ML and the AP directions using previously described methods10, 18.
Subjects walked six times in barefoot over the pressure plate (Footscan, RSscan International, Olen, Belgium) with 120 Hz sampling rate19. Three walks for each foot were recorded and printed. Each print consisted of a time peak-force curve for eight regions of interest on the foot. The regions of interest, which were analyzed automatically by the system software, were medial heel (HM), lateral heel (HL), 1st to 5th metatarsal heads(M1~M5), and toes(T1). The time variables were calculated as the ratio of time from the start of the stance to peak force under the region of interest and the total stance time. The peak force variables were calculated as the ratio of the peak force under the region of interest, and were normalized by the body weight20
Isokinetic strength measurement
As described in TW Kaminski’s research21, isokinetic strength was assessed with a Biodex isokinetic dynamometer (Biodex Medical Systems Inc, Shirley, NY). Each subject’s foot was securely fastened on the biodex chair, with the hip angle 80◦ flexion (0◦ neutral position) and 20°to 30° of knee flexion. Each subject was allowed three submaximal (50% capacity) warm-up repetitions at each velocity to become familiar with the isokinetic test procedure, then performed three maximal concentric test repetitions at 60 and 120°/s on both ankles. The resting interval was approximately one minute between tests for each motion, velocity, and side. At the end of testing, peak torque data were extracted from the torque curves.
Balance training protocol
As was shown in table 2, the balance training protocol was designed based on the widely used protocol from the published papers22-23. The protocol includes single-legged stance, wobble board, resistant band and hop exercises and so on.
Table 2. The balance training protocol.
Exercise
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Description
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Progression
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Single-legged stance
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Performed up to 60s per repetition for up to 3 repetitions.
Performed with eyes opened and eyes closed
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Progressed when participants could complete a 60-s trial without a loss of balance.
Increased no. of repetitions by 1
Changed surface from floor to using the Dyna-Disca.
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Wobble board
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Slowly moved the board in the plantar- flexion/dorsiflexion and inversion/eversion directions without letting the board contact the floor.
Performed up to 10 repetitions in each direction.
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Progressed when participant could complete the task without upper extremity support.
Added rotational directions.
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Steamboats
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Tied a 48-in Thera-band around the unstable ankle.
Positioned stance foot 27-in from where Thera-band was tied.
Performed up to 3 sets of 15 repetitions in each direction (hip flexion, extension, abduction, adduction).
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Progressed when participants could complete the repetitions without a loss of balance or fatigue.
Increased no. of repetitions from 10 to 15.
Progressed to next level of resistance with the Thera-band.
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Single-legged hop
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Hopped as far as comfortable in the anterior direction.
Performed up to 15 repetitions.
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Progressed when participants could perform the task with minimal ankle and hip motion and no loss of balance on landing.
Increased no. of repetitions from 5 to 10 to 15.
Encouraged increased distance to participants’ tolerance.
Progressed to medial, lateral, and posterior directions.
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Quadrant hop
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Hopped in numbered squares clockwise and counterclockwise while maintaining single-legged stance.
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Progressed when participants could complete 2 sets of 5 hops without a loss of balance or fatigue
Made unanticipated directional changes where investigator randomly called out numbers.
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Single-legged ball catch
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Performed up to 3 sets of 20 tosses
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Progressed when participants could perform 20 tosses without a loss of balance.
Tossed ball outside participants base of support.
Performed during stance on a DynaDisc.
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Toe touch down
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Maintained single-legged stance on a step while lowering the unstable ankle in the anterior, posterior, medial, and lateral directions until the foot contacted floor.
Performed up to 3 sets of 10 repetitions.
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Progressed when participants could complete all trials without a loss of balance and with good lower extremity alignment (no eversion collapse)
Increased no. of repetitions from 5 to 10.
Increased height of step from 4 in to 12 in in 2-in increments
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Hop ups and downs
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Hop off step and landed in single-legged stance on floor.
Performed up to 3 sets of 10 repetitions.
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Progressed when participants could complete all hops without a loss of balance or fatigue.
Increased no. of repetitions from 5 to 10.
Increased height of step from 4 in to 12 in in 2-in increments
Changed direction of hop.
Hopped up onto step.
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a Exertools, Petaluma, CA. b The Hygenic Corporation, Akron, OH
Risk factors analysis
Based on the ankle sprain recurrence after the balance training program through one year, the patients were divided into the sprain recurrence group and control group. The pre-training variables for each patient was used to analyze the risk factor for the sprain recurrence after the balance training.
Data analysis
The self- reported function (FAAM and CAIT), postural control measures (TTB measures and COP-based measures, plantar pressure measures) were analyzed separately at pre-training, post-training, 6 months and 1 year. Paired sample t test was used to assess changes in the dependent measures before and after balance training. Shapiro-Wilk test was used to assess Normality of data. Univariate analysis and multivariable logistic regression model were used to explore the risk factors of sprain recurrence after the balance training, Alpha level was set a priori at p < 0.05. An a priori power analysis was completed using data from a previous study24 in which the researchers examined the effects of a similar balance-training program. Based on an α level of .05, a power of 0.95, and an effect size of 0.97 determined by the FAAM-Sport, 16 participants were needed. Therefore, we enrolled 20 participants to account for up to 20% attrition.