Erik A. Wikstrom

Selection criteria for patients with chronic ankle instability in controlled research: a position statement of the international ankle consortium

The International Ankle Consortium is an international community of researchers and clinicians whose primary scholastic purpose is to promote scholarship and dissemination of research-informed knowledge related to pathologies of the ankle complex. The constituents of the International Ankle Consortium and other similar organizations have yet to properly define the clinical phenomenon known as chronic ankle instability (CAI) and its related characteristics for consistent patient recruitment and advancement of research in this area. Although research on CAI and awareness of its impact on society and healthcare systems have grown substantially in the last 2 decades, the inconsistency in participant/patient selection criteria across studies presents a potential obstacle to addressing the problem properly. This major gap within the literature limits the ability to generalize this evidence to the target patient population. Therefore, there is a need to provide standards for patient/participant selection criteria in research focused on CAI, with justifications using the best available evidence.

Postural control differs between those with and without chronic ankle instability

Despite a history of a lateral ankle sprain, some individuals (copers) return to high-level activities (i.e. jumping, pivoting) without recurrent injury or loss of function while others develop chronic ankle instability (CAI). Understanding the differences between these groups may provide insight into the mechanisms of CAI. The objectives of this investigation were to: (1) compare traditional center of pressure [COP], time-to-boundary [TTB], and center of pressure-center of mass [COP-COM] moment arm measures of postural control among controls, established copers, and subjects with CAI and (2) determine the accuracy of these postural control measures at discriminating between established copers and subjects with CAI using receiving operating characteristic curves. 48 subjects (control=16, coper=16, CAI=16) completed two, 30-s trials of single-leg stance on a force plate with their eyes open. Coper and CAI subjects stood on their involved limb while controls stood on a matched limb. The results indicated that mediolateral (p<0.01) and anteroposterior (p<0.01) COP velocity was greater in individuals with CAI relative to both copers and controls. Similarly, the peak COP-COM moment arm in the anteroposterior direction (p<0.01) and the resultant mean COP-COM moment arm (p<0.01) were increased in individuals with CAI relative to copers. These measures also reached asymptotic significance (p<0.05) indicating that they successfully discriminated between established copers and individuals with CAI.

Chronic ankle instability alters central organization of movement.

Background Chronic ankle instability alters spinal level sensorimotor function and is hypothesized to alter supraspinal motor control mechanisms. Gait initiation is a functional task modulated by supraspinal pathways, but the effect of chronic ankle instability, a peripheral musculoskeletal impairment, on gait initiation and thus supraspinal motor control mechanisms remains unknown. Purpose This study was conducted to determine if supraspinal aspects of motor control are altered in subjects with chronic ankle instability. Study Design Controlled laboratory study. Methods Subjects with chronic ankle instability (5 males, 15 females; age, 20.5 ± 1.0 years; height, 169.8 ± 9.8 cm; weight, 74.2 ± 20.2 kg) and uninjured controls (4 males, 16 females; age, 20.85 ± 1.6 years; height, 164.3 ± 7.9 cm; weight, 64.2 ± 10.62 kg) completed 5 gait initiation trials for each leg at a self-selected pace. The resulting trajectory of the center of pressure trace was investigated and peak center of pressure excursions in the anteroposterior and mediolateral directions, peak resultant center of pressure excursions, and average direction-specific velocities were calculated. Results Significant group × limb interactions were noted during the first (resultant center of pressure displacement [F1,37 = 4.60, P = .04]) and second (mediolateral center of pressure displacement [F1,37 = 3.82, P = .05]) period of gait initiation. Center of pressure displacement was reduced (impaired) in the involved limb of the chronic ankle instability group (resultant, 0.29 ± 0.02; mediolateral, 0.72 ± 0.02) relative to the uninvolved limb of the chronic ankle instability group (resultant, 0.32 ± 0.02; mediolateral, 0.76 ± 0.02) and both limbs of the control group (resultant, 0.32 ± 0.02; mediolateral, 0.74 ± 0.02) when the involved limb of the chronic ankle instability group served as the initial stance limb. Conclusion These interactions suggest that supraspinal motor control mechanisms are altered in subjects with chronic ankle instability to place a greater emphasis on reducing the postural demands on the involved limb. Clinical Relevance These changes suggest that supraspinal adaptations to motor control may be an important contributor to the underlying neurophysiologic mechanism of chronic ankle instability. The presence of supraspinal adaptations in subjects with chronic ankle instability also indicates that health care providers and rehabilitation specialists treat chronic ankle instability as a global/central and not just a local/peripheral injury.

Dynamic postural control but not mechanical stability differs among those with and without chronic ankle instability

The purpose of this investigation was to compare dynamic postural control and mechanical ankle stability among patients with and without chronic ankle instability (CAI) and controls. Seventy‐two subjects were divided equally into three groups: uninjured controls, people with previous ankle injury but without CAI, and people with CAI. Subjects completed a single‐leg hop‐stabilization task, and then had an anterior drawer test and lateral ankle radiograph performed bilaterally. The dynamic postural stability index was calculated from the ground reaction forces of the single‐leg hop‐stabilization task. Ankle joint stiffness (N/m) was measured with an instrumented arthrometer during the anterior drawer test, and fibula position was assessed from the radiographic image. Patients with previous ankle injuries but without CAI demonstrated higher frontal plane dynamic postural stability scores than both the uninjured control and CAI groups (P<0.01). Patients with and without CAI had significantly higher sagittal plane dynamic postural stability scores (P<0.01) and increased ankle joint stiffness (P=0.045) relative to the control group. The increased frontal plane dynamic postural control may represent a component of a coping mechanism that limits recurrent sprains and the development of CAI. Mechanical stability alterations are speculated to result from the initial ankle trauma.

Measurement and evaluation of dynamic joint stability of the knee and ankle after injury

Injuries to the lower extremity, specifically the knee and ankle joints of the human body can occur in any athletic event and are most prevalent in sports requiring cutting and jumping manoeuvres. These joints are forced to rely on the dynamic restraints to maintain joint stability, due to the lack of bony congruence and the inability of the static restraints to handle the forces generated during functional tasks. Numerous variables (proprioception, postural control, electromyography, kinetics/kinematics, dynamic stability protocols) have been measured to better understand how the body maintains joint stability during a wide range of activities from static standing to dynamic cutting or landing from a jump. While the importance of dynamic restraints is not questioned, a recent impetus to conduct more functional or sport-specific testing has emerged and placed a great deal of emphasis on dynamic joint stability and how it is affected by lower extremity injuries. Evidence suggests that surgery and aggressive rehabilitation will not necessarily restore the deficits in dynamic joint stability caused by injury to the anterior cruciate ligament or lateral ankle ligaments. In today’s athletic society, there is a major push to return athletes to play as quickly as possible. However, the ramifications of those decisions have not been fully grasped. If an athlete is not fully recovered, a quick return to play could start a vicious cycle of chronic injuries or permanent disability.

Self-Assessed Disability and Functional Performance in Individuals With and Without Ankle Instability: A Case Control Study

STUDY DESIGN Single-blind case-control study. OBJECTIVE To compare functional performance and self-assessed disability scores among individuals with and without chronic ankle instability (CAI) and uninjured controls. BACKGROUND After an acute lateral ankle sprain, CAI develops in 40% to 75% of all individuals. However, some individuals, copers, maintain high-level activities after an ankle sprain and do not develop CAI. Studying differences between copers and those with CAI is the first step in developing a clinical battery of tests that can accurately determine which individuals are more likely to develop CAI after an acute lateral ankle sprain. METHODS AND MEASURES Participants were 24 active adults with unilateral CAI (mean +/- SD age, 21.7 +/- 2.8 years), 24 copers (20.8 +/- 1.5 years), and 24 uninjured controls (21.8 +/- 2.6 years). Participants completed 3 questionnaires of self-assessed disability: (1) Foot and Ankle Disability Index, (2) Foot and Ankle Disability Index-Sport, and (3) a questionnaire of ankle function. Four hop tests were also completed: (1) figure-8 hop, (2) side-to-side hop, (3) triple-crossover hop, and (4) single-leg hop for distance. RESULTS Self-assessed disability was significantly different among groups (P<.001), but hop test scores (P = .259) were not. Those with CAI had greater self-assessed disability than copers and uninjured controls. Copers and uninjured controls did not differ in self-assessed disability or functional performance. CONCLUSIONS Self-assessed disability is significantly greater in those with CAI than copersand uninjured controls. However, functional performance, measured by hop tests, did not differ among groups.

Gait termination control strategies are altered in chronic ankle instability subjects.

UNLABELLED Despite the high incidence of chronic ankle instability (CAI), the underlying neurophysiologic mechanism is unknown. Evidence suggests that both feed-forward and feedback mechanisms may play a role. However, no investigation has examined both control mechanisms during the same movement task in the same cohort of CAI patients. PURPOSE To determine the neuromuscular and biomechanical control alterations present in CAI patients during planned (feed-forward) and unplanned (feedback) gait termination. METHODS Twenty subjects with CAI and 20 uninjured controls completed planned and unplanned gait termination protocols. Both tasks began with subjects walking at a self-selected speed across a 12-m walkway. Unplanned gait termination required subjects to stop during randomly selected trials on two adjacent force plates when cued. Planned gait termination required purposeful stopping on the force places. Propulsive and braking force magnitude and the dynamic postural stability index were calculated from the resulting ground reaction forces. In addition, muscle activity from the soleus, tibialis anterior, and gluteus medius was collected bilaterally. RESULTS Both maximum propulsive (CAI = 99.8 +/- 40.8 N, control = 88.6 +/- 33.6 N) and braking (CAI = 207.1 +/- 80.9 N, control = 161.6 +/- 62.2 N) forces were significantly higher in the CAI group. The dynamic postural stability index revealed higher scores in the CAI group (0.24 +/- 0.03) compared with the control group (0.22 +/- 0.03). Muscle activation of the soleus and tibialis anterior differed during unplanned and planned gait termination between groups (P < 0.05) and between the limbs of the CAI group (P < 0.05). CONCLUSIONS Altered biomechanical strategies during both planned and unplanned gait termination indicate that patients with CAI have alterations in feed-forward neuromuscular control and suggest the presence of feedback neuromuscular control deficits.

Talar Positional Fault in Persons With Chronic Ankle Instability

OBJECTIVE To determine whether sagittal plane talar position differs between uninjured controls and individuals with chronic ankle instability (CAI) using lateral ankle radiographs. DESIGN Single-blind case control. SETTING University-based sports medicine research laboratory. PARTICIPANTS University students (N=48) volunteered to participate. Twenty-four uninjured controls (12 men, 12 women; mean +/- SD, 21.8+/-2.6y; 170+/-10cm; 73+/-16kg), and 24 adults with CAI (12 men, 12 women; 21.7+/-2.8y; 175+/-13cm; 71+/-13kg) participated. INTERVENTION A single nonweight-bearing lateral radiograph was taken of each ankle. Subjects were positioned side lying with the hip and knee in a neutral position in the transverse plane and the ankle joint in a neutral position (90 degrees of dorsiflexion, 0 degrees of inversion/eversion). MAIN OUTCOME MEASURE The sagittal plane talar position was calculated as the distance between the most anterior margin of the inferior tibia and the most anterior margin of the talar dome in millimeters for each radiograph. RESULTS Talar position was significantly more anterior in the involved CAI limb (3.69+/-1.37mm) than the uninvolved CAI limb (2.98+/-1.61mm; P=.03). Additionally, an anterior talar position was significantly greater in the involved CAI limb than the matched control limb (2.65+/-1.24cm; P<.01). No differences were found between the uninvolved CAI limb and the matched control group limb (P=.57) or between the limbs of the uninjured control group (P=.75). Intratester reliability was found to be .90, while intertester reliability was .78. CONCLUSIONS An anterior talar positional fault is present in the involved limb of individuals with CAI relative to their uninvolved limb and compared with the matched limb of a control group. The talar position measurement technique has excellent intratester and intertester reliability.

Gender and Limb Differences in Dynamic Postural Stability During Landing

ObjectiveTo determine if gender and limb dominance affect dynamic postural stability and vertical ground reaction force data during jump landings. Secondary objective was to assess the reliability of the dynamic postural stability index (DPSI). DesignA mixed model (2 gender×2 limb) repeated measures design was used to determine the effects of gender and limb dominance on dynamic postural stability. Subjects were required to perform a two-legged jump to a height equivalent of 50% of their maximum vertical leap, land on a single-leg and balance for three seconds. SettingSports Medicine Research Laboratory. ParticipantsForty healthy subjects (20 men, 20 women) participated in this investigation. Main Outcome MeasuresThe DPSI and its directional components quantified dynamic postural stability during a single-leg jump landing. Normalized vertical ground reaction force data quantified energy absorption. ResultsDPSI values revealed that females had significantly different dynamic postural stability as compared to males in the vertical plane [T (78)=−4.2, P<0.01], and in the composite score (dynamic postural stability index) [T (78)=−6.3, P<0.01]. In addition, females had significantly higher peak vertical ground reaction forces [T (78)=−13, P=0.01] than males. The DPSI also showed excellent reliability (ICC=0.96), with a 95% confidence interval ranging from 0.94 to 0.97. ConclusionsThe results indicate that females have higher dynamic postural stability scores in the vertical direction as well as the composite score. This suggests that females used different dynamic postural stability strategies than males. There were no side-to-side dynamic postural stability differences between healthy contralateral limbs.

Evidence review for the 2016 International Ankle Consortium consensus statement on the prevalence, impact and long-term consequences of lateral ankle sprains.

Lateral ankle sprains (LASs) are the most prevalent musculoskeletal injury in physically active populations. They also have a high prevalence in the general population and pose a substantial healthcare burden. The recurrence rates of LASs are high, leading to a large percentage of patients with LAS developing chronic ankle instability. This chronicity is associated with decreased physical activity levels and quality of life and associates with increasing rates of post-traumatic ankle osteoarthritis, all of which generate financial costs that are larger than many have realised. The literature review that follows expands this paradigm and introduces emerging areas that should be prioritised for continued research, supporting a companion position statement paper that proposes recommendations for using this summary of information, and needs for specific future research.