Analysis of the effects of normal walking on ankle joint after acute inversion ankle sprain
Computer model of an individual with an injured lateral ankle ligaments (LAL) representing a significant inversion ankle sprain showed altered ankle joint kinematics i.e. increased contact pressures and strains during normal walking.
Acute ankle sprain is a common sports injury in which the ligaments of the ankle are partially or completely torn due to sudden and abnormal stretching. Up to 80% of sprains are associated with an inversion mechanism. Lateral ankle ligaments (LALs) are most frequently injured by inversion ankle sprain.
Acute ankle sprain is a common sports injury in which the ligaments of the ankle are partially or completely torn due to sudden and abnormal stretching. Up to 80% of sprains are associated with an inversion mechanism. Lateral ankle ligaments (LALs) are most frequently injured by inversion ankle sprain. A common LAL injury is injury of the anterior talofibular ligament (ATFL), often accompanied by the injury of calcaneofibular ligament (CFL) or both CFL and posterior talofibular ligament (PTFL). Non-operative treatments are used for these LAL injuries and on failing, LAL injuries may result into lateral ankle instability causing cartilage degeneration or ankle joint osteoarthritis.
The effects of deficient or intact ATFL on cartilage contact conditions under weight bearing conditions has been studied but there is a need to study the effects of normal walking with an injured LAL on cartilage contact conditions.
Rationale behind research
- Studies have shown valuable data on in vivo ankle joint cartilage contact conditions with an intact or deficient ATFL, underweight bearing conditions but did not show effects of normal walking with an injured LAL ankle joint on in vivo cartilage contact situation.
To show the causal relationship between normal walking on injured LAL ankle joints resulting from acute inversion ankle sprain and ankle joint characteristics
NOTE: This was a different study in which complex 3D finite element (FE) model of a foot with an intact ankle joint was constructed. Using the intact ankle model, two different ATFL deficient models and three LAL-ruptured models (ATFL, ATFL + CFL and ATFL+ CFL + PTFL ruptures) were fabricated for various LAL injury types. FE simulations were carried out using these models to evaluate ankle cartilage contract pressures and strains as well as in silico tibiotalar joint motions under normal walking conditions. The four stance phases of the gait cycle-heel strike, foot flat, mid stance and push off were simulated. Also, barefoot walking experiments were carried out to provide the boundary conditions for the FE simulations and to validate the simulation results.
- Contact pressure distributions, peak contact pressures, peak contact strains, anteroposterior translation, mediolateral translation
- Contact Pressure Distributions: With the progression of the walking phases, the contact pressures on the cartilage gradually increased and contact regions expanded in both models. In the ATFL- ruptured ankle joint model, the concentrated contact pressures increased at each stance phase and the concentrated pressure regions were more medially translated at the foot flat and midstance phases compared with those of intact model.
- Peak Contact Pressures: In the intact model, the peak contact pressures at the foot flat, midstance, and push off stance phases were 3.95, 6.18, and 16.02 MPa, respectively. In the two ATFL deficient models, these peak values increased gradually (4.87, 6.54, and 16.37 MPa, respectively, in the ATFL deficient #1 model and 5.37, 7.12, and 16.79 MPa, respectively, in the ATFL-deficient #2 model). The values of the ATFL-ruptured model were 6.01, 8.33, and 17.24 MPa, which were higher than those of the intact and two ATFL-deficient models.
- Peak Contact Strains: Similar to the peak contact pressures, a rapid increase in the values was observed at the push off stance phase. There were no significant differences in peak contact strain among the models at the heel strike stance phase, which was around 0.015–0.017. In the intact model, the values were 0.144, 0.219, and 0.681, at the foot flat, midstance, and push off phases. The ATFL-deficient #1 (0.150, 0.224, and 0.705), ATFL-deficient #2 (0.178, 0.238, and 0.793), and ATFL-ruptured (0.186, 0.241, and 0.838) models showed an increase in those values compared with those of the intact model. However, at the push off phase, the value was slightly increased to 0.883 (5% increase).
- Anteroposterior Translation: In the intact ankle model, the talus was translated anteriorly, and the translation increased as the walking phases progressed (3.67, 5.79, and 14.42 mm, respectively). At each stance phase, positive differences in the anterior translation were observed in the ATFL-deficient #1 (0.05, 0.05, and 0.12, respectively), ATFL-deficient #2 (0.19, 0.17, and 0.25, respectively), and ATFL-ruptured (0.26, 0.25 and 0.35, respectively) models. The differences at all phases in the ATFL + CFL-ruptured and all ruptured models were almost the same as those of the ATFL-ruptured model. The ATFL-deficient #1 model showed a smaller translation than ATFL-deficient #2 model. The translations of the ATFL + CFL ruptured and all ruptured ankle models were almost the same as those of the ATFL-ruptured model.
- Mediolateral Translation: In the intact ankle model, the talus was medially translated at the foot flat phase (0.07 mm), and the translation increased at the midstance phase (0.14 mm). At the push off phase, contralateral translation was observed (lateral translation of 0.1 mm). In addition, at the push off phase, contralateral translations from the injured LAL models were observed. However, all the mediolateral translations and their differences at each stance phase were very small compared with those of the anteroposterior translation of the talus.
Computer model of an individual with an injured LAL representing a significant inversion ankle sprain showed altered ankle joint kinematics during normal walking. The ATFL ruptured ankles showed a higher likelihood of experiencing increased ankle joint contact pressure, strain and translations than ATFL deficient ankles. ATFL + CFL ruptured and all ruptured ankles showed a similar likelihood as the ATFL ruptured ankles.
The results are consistent with the results from another study showing the significant increase of the anterior translation in ATFL injury ankle compared to the intact ankle. Overall a deficient ATFL and LAL rupture increased contact pressures and strains during normal walking.