Acute Ankle Sprain in a Mouse Model

Effects of chronic ankle instability after grade I ankle sprain on the post-traumatic osteoarthritis

BACKGROUND

Untreated acute ankle sprains often result in chronic ankle instability (CAI) and can ultimately lead to the development of post-traumatic osteoarthritis (PTOA). At present, a typical animal model of ankle instability in mice is established by transecting the ligaments around the ankle joint. This study aimed to establish a grade I acute ankle sprain animal model by rapid stretching of peri-ankle joint ligaments. Furthermore, we tried to explore the pathophysiological mechanism of ankle osteoarthritis.

METHODS

In all, 18 male C57BL/6 J mice (7 weeks) were randomly divided into three groups: calcaneofibular ligament (CFL) laxity group, deltoid ligament (DL) laxity group, and SHAM group. One week after the surgical procedure, all mice were trained to run in the mouse rotation fatigue machine daily. The mice were tested on the balance beam before surgery and three days, 4 weeks, 8 weeks, and 12 weeks after surgery. Footprint analyses were performed on each mouse before surgery and 12 weeks after surgery. Micro-CT scanning was then performed to evaluate the degeneration of ankle joints and histological staining was performed to analyze and evaluate PTOA caused by ankle joint instability.

RESULTS

After surgery, the mice in the CFL and DL laxity groups took longer to cross the balance beam and slipped more often than those in the SHAM group (p < 0.05). The step length and width in the CFL and DL laxity groups were significantly shorter and smaller than those in the SHAM group 12 weeks after surgery (p < 0.05). There was a significant increase in the bone volume fraction (BV/TV) in the CFL and DL laxity groups compared with the SHAM group (p < 0.05). Histological staining results suggested obvious signs of PTOA in the CFL and DL laxity groups.

CONCLUSIONS

Based on CFL and DL laxity in a mouse ankle instability model, this study suggests that grade I ankle sprain can contribute to chronic ankle instability, impair motor coordination and balance, and eventually lead to PTOA of ankle with significant degeneration of its adjacent joints.

Brain regulates weight bearing bone through PGE2 skeletal interoception: implication of ankle osteoarthritis and pain

Bone is a mechanosensitive tissue and undergoes constant remodeling to adapt to the mechanical loading environment. However, it is unclear whether the signals of bone cells in response to mechanical stress are processed and interpreted in the brain. In this study, we found that the hypothalamus of the brain regulates bone remodeling and structure by perceiving bone prostaglandin E2 (PGE2) concentration in response to mechanical loading. Bone PGE2 levels are in proportion to their weight bearing. When weight bearing changes in the tail-suspension mice, the PGE2 concentrations in bones change in line with their weight bearing changes. Deletion of cyclooxygenase-2 (COX2) in the osteoblast lineage cells or knockout of receptor 4 (EP4) in sensory nerve blunts bone formation in response to mechanical loading. Moreover, knockout of TrkA in sensory nerve also significantly reduces mechanical load-induced bone formation. Moreover, mechanical loading induces cAMP-response element binding protein (CREB) phosphorylation in the hypothalamic arcuate nucleus (ARC) to inhibit sympathetic tyrosine hydroxylase (TH) expression in the paraventricular nucleus (PVN) for osteogenesis. Finally, we show that elevated PGE2 is associated with ankle osteoarthritis (AOA) and pain. Together, our data demonstrate that in response to mechanical loading, skeletal interoception occurs in the form of hypothalamic processing of PGE2-driven peripheral signaling to maintain physiologic bone homeostasis, while chronically elevated PGE2 can be sensed as pain during AOA and implication of potential treatment.

Characterization of pain-related behaviors and gene expression profiling of peripheral sensory ganglia in a mouse model of acute ankle sprain

Introduction

Lateral ankle sprain (LAS) is a very common type of joint injury. It occurred with high incidence among general population and especially among individuals participating sports and outdoor activities. A certain proportion of individuals who once developed LAS may suffer persistent ankle pain that affects daily activities. However, the mechanisms underlying LAS-induced pain still remained largely unknown.

Methods

We established a LAS mouse model and systematically evaluated the pain-related behaviors in this mouse model. RNA sequencing (RNA-Seq), combined with bioinformatics analysis, was undertaken to explore gene expression profiles. Immunostaining was used to study glial cell and neuron activation in ipsilateral spinal cord dorsal horn (SCDH) of LAS model mice. Ibuprofen was used to treat LAS model mice.

Results

The LAS model mice developed obvious signs of mechanical and heat hypersensitivities as well as gait impairments in ipsilateral hind paws. Besides, LAS model mice developed signs of pain-related emotional disorder, including pain-induced aversion. By RNA-Seq, we were able to identify certain differentially expressed genes and signaling pathways that might contribute to pain mechanisms of LAS mouse model. In addition, LAS model mice showed increased c-Fos and p-ERK immunoreactivity as well as astrocyte and microglia overactivation in ipsilateral spinal cord dorsal horn, indicating central sensitization might occur. Finally, LAS model mice respond to ibuprofen, a drug clinically used to treat ankle sprain pain.

Conclusion

Our study found LAS model mice may be used as a preclinical animal model for screening novel targets or therapies for ankle sprain. Thus, the study may further help to understand molecular mechanisms contributing to ankle sprain-induced pain.

Mouse model of subtalar post-traumatic osteoarthritis caused by subtalar joint instability

BACKGROUND

Common ankle sprains are often accompanied by injury to the subtalar joint, which eventually leads to subtalar joint instability. Because the clinical manifestations for subtalar joint instability are similar to ankle joint injuries, these are often overlooked. This study aimed to establish an animal model of subtalar joint instability to study post-traumatic osteoarthritis of the subtalar joint caused by long-term subtalar joint instability and to provide a reference for future clinical research on chronic subtalar joint instability.

METHODS

In all, 24 C57BL/6 male mice were randomly divided into three groups: Sham, cervical ligament (CL) transection and CL + calcaneofibular ligament (CFL) transection groups. One week after surgical operation, all mice were trained to run in the mouse rotation fatigue machine every day. During this period, a balance beam test was used to evaluate the motor level and coordination ability of the mice before the operation and three days, one week, four weeks, eight weeks, and twelve weeks after operation. Further, post-traumatic osteoarthritis of the subtalar joint was quantified via micro-CT and histological staining.

RESULTS

The mice in the partial ligament transection group took significantly longer than those in the Sham group to pass through the balance beam and showed an increased number of hindfoot slips. Micro-CT analysis showed that the subtalar bone volume fraction in the CL + CFL transection group and CL transection group was 5.8% and 2.8% higher than that in the Sham group, respectively. Histological staining showed obvious signs of post-traumatic osteoarthritis (PTOA) in the subtalar joint of the ligament transection group.

CONCLUSIONS

The transection of CL and CL + CFL can cause instability of the subtalar joint in mice, resulting in a decrease in motor coordination, and long-term instability of the subtalar joint in mice can cause PTOA of the subtalar joint, which is manifested as destruction and loss of articular cartilage.

Longitudinal neuroplasticity after ankle sprain in mice: A voxel-based morphometry study on 11.7T MRI

Lateral ankle sprains (LAS) might lead to joint sensory deafferentation, which induces maladaptive neuroplasticity, especially the morphological atrophy of the cerebellar vermis. However, longitudinal evidence on the causality of injury and neural differences is still lacking. To this end, this study aimed to determine whether the morphology of the central nervous system would be altered before and after ligament transection in LAS mouse models. A total of 40 C57BL/6 mice were randomly divided among the LAS, Sham and Blank groups. We repeatedly performed the balance beam test and neural voxel-based morphometry (VBM) measurements using an 11.7 T magnetic resonance imaging before and 2 months after the surgery. The results showed that for balance outcomes, the LAS group had a significantly longer time and more slips of the balance beam tests compared with the Sham and Blank groups at 2 months after surgery, with no significant difference among the three groups before surgery. Regarding the VBM analysis, the LAS group showed significantly lower VBM values in the central lobule III of the cerebellar vermis and medial amygdalar nucleus (MEA) compared with the Sham and Blank groups after surgery, with no significant difference among the three groups before surgery. In conclusion, lateral ligament injuries might lead to morphological atrophy of the cerebellar vermis in animal models, which might pave the way for the pathological process of ankle instability after LAS.

A new mouse model of ankle instability induced by multiple mechanical sprains with controlled inversion angle and speed

Ankle sprain occurs by a sudden and extreme inversion and plantarflexion at the ankle joint to cause ligamentous injuries. A portion of ankle sprain patients experience recurrent ankle sprains and develop chronic ankle instability (CAI). The present CAI animal models are single events with severe ligamentous injury using surgical transection of ligaments or manually overextending the ankle.

Purpose: To simulate the mechanical and recurrent sprain injuries in CAI patients, we established a new ankle instability model with multiple ankle injuries using a self-designed machine to sprain the ankle with a controlled inversion angle and speed.

Methods: Male C57BL/6J mice were used and respectively subjected to a sham operation, calcaneofibular ligament (CFL) transection, and mechanical ankle sprains. Three mechanical sprains were performed on the 13th and 185th day after the initial mechanical ankle sprain.

Results: The first mechanical sprain and CFL transection induced ankle injury as indicated by an average of a 62% decrease in ankle pressure pain threshold and a 114% increase in the ankle thickness compared with the contralateral untreated ankle. The second and third mechanical sprains induced recurrent ankle injuries. The foot slips during beam tests were increased after mechanical ankle sprains but not after CFL transection, indicating the induction of motor balance deficits. Multiple mechanical ankle sprains induced significant gait changes in longer duration of stance (an average of 194% increase), swing (134%), and step cycle (147%) compared with CFL transection or sham operation, and slower walking speed (78% reduction) and shorter step distance (91%) after the third sprain.

Conclusion: These results elucidate that multiple mechanical sprains, which induce recurrent ankle injuries, balance deficits, and gait changes, are a good model for investigating the mechanisms of CAI induced by recurrent sprain injuries.

Ligamentous injury-induced ankle instability causing posttraumatic osteoarthritis in a mouse model

BACKGROUND

This study aims to explore the relationship between surgically-induced ankle instability and posttraumatic osteoarthritis (PTOA) in a mouse model, and to provide reference for clinical practice.

RESULTS

Ligamentectomy was performed on 24 eight-week-old male C57BL/6 J mice, which were divided into three groups. Both the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL) were severed in the CFL + ATFL group, while only the CFL was removed in the CFL group. The SHAM group was set as the blank control group. A wheel-running device was used to accelerate the development of ankle osteoarthritis (OA). Balance measurement, footprint analysis, and histological analysis were used to assess the degree of ankle instability and OA. According to the balance test results, the CFL + ATFL group demonstrated the highest number of slips and the longest crossing beam time at 8 weeks postoperatively. The results of gait analysis exhibited that the CFL + ATFL group had the most significant asymmetry in stride length, stance length, and foot base width compared to the CFL and SHAM groups. The OARSI score of the CFL + ATFL group (16.7 ± 2.18) was also much higher than those of the CFL group (5.1 ± 0.96) and the SHAM group (1.6 ± 1.14).

CONCLUSION

Based on the mouse model, the findings indicate that severe ankle instability has nearly three times the chance to develop into ankle OA compared to moderate ankle instability.

Exosomes derived from platelet-rich plasma administration in site mediate cartilage protection in subtalar osteoarthritis

Subtalar osteoarthritis (STOA) is often secondary to chronic ankle sprains, which seriously affects the quality of life of patients. Due to its etiology and pathogenesis was not studied equivocally yet, there is currently a lack of effective conservative treatments. Although they have been used for tissue repair, platelet-rich plasma-derived exosomes (PRP-Exo) have the disadvantage of low retention and short-lived therapeutic effects. This study aimed to determine whether incorporation of PRP-Exo in thermosensitive hydrogel (Gel) increased their retention in the joint and thereby playing a therapeutic role on STOA due to chronic mechanical instability established by transecting lateral ligaments (anterior talofibular ligament (ATFL)/calcaneal fibular ligament (CFL)). PRP-Exo incorporated Gel (Exo-Gel) system, composed of Poloxamer-407 and 188 mixture-based thermoresponsive hydrogel matrix in an optimal ratio, was determined by its release ability of Exo and rheology of Gel response to different temperature. The biological activity of Exo-Gel was evaluated in vitro, and the therapeutic effect of Exo-Gel on STOA was evaluated in vivo. Exo released from Exo-Gel continuously for 28 days could promote the proliferation and migration of mouse bone mesenchymal stem cells (mBMSCs) and chondrocytes, at the same time enhance the chondrogenic differentiation of mBMSCs, and inhibit inflammation-induced chondrocyte degeneration. In vivo experiments confirmed that Exo-Gel increased the local retention of Exo, inhibited the apoptosis and hypertrophy of chondrocytes, enhanced their proliferation, and potentially played the role in stem cell recruitment to delay the development of STOA. Thus, Delivery of PRP-Exo incorporated in thermosensitive Gel provides a novel approach of cell-free therapy and has therapeutic effect on STOA.

Graphical Abstract

A mouse model of ankle-subtalar joint complex instability induced post-traumatic osteoarthritis

BACKGROUND

Ankle-subtalar joint complex instability is not uncommonly presented in the clinic, but symptoms and signs similar to other conditions can easily lead to its misdiagnosis. Due to the lack of appropriate animal models, research on ankle-subtalar joint complex instability is limited. The aims of the present study were to establish an animal model of ankle-subtalar joint complex instability in mice and to explore its relationship with post-traumatic osteoarthritis (PTOA).

METHODS

Twenty-one male C57BL/6J mice were randomly divided into three groups: SHAM group (sham surgery group), transected cervical ligament + anterior talofibular ligament (CL+ATFL) group, and transected cervical ligament + deltoid ligament (CL+DL) group. Two weeks after surgery, all mice underwent cage running training. Balance beam and gait tests were used to evaluate the changes in self-movement in the mice after ankle-subtalar ligament injury. Micro-CT and histological staining were used to evaluate the progress of PTOA.

RESULTS

Compared with the SHAM group, balance and gait were affected in the ligament transection group. Twelve weeks after surgery, the time required to cross the balance beam in the CL+ATFL group was 35.1% longer and the mice slipped 3.6-fold more often than before surgery, and the mean step length on the right side was 7.2% smaller than that in the SHAM group. The time required to cross the balance beam in the CL+DL group was 32.1% longer and the mice slipped 3-fold more often than prior to surgery, and the average step length on the right side was 5.6% smaller than that in the SHAM group. CT images indicated that 28.6% of the mice in the CL+DL group displayed dislocation of the talus. Tissue staining suggested that articular cartilage degeneration occurred in mice with ligament transection 12 weeks after surgery.

CONCLUSIONS

Transected mice in the CL+ATFL and CL+DL groups displayed mechanical instability of the ankle-subtalar joint complex, and some mice in the CL+DL group also suffered from talus dislocation due to ligament injury leading to loss of stability of the bone structure. In addition, as time progressed, the articular cartilage displayed degenerative changes, which affected the ability of animals to move normally.

Regeneration of grade 3 ankle sprain, using the recombinant human amelogenin protein (rHAM+ ) in a rat model

Lateral ligament tears, also known as high-grade ankle sprains, are common, debilitating, and usually heal slowly. Ten to thirty percent of patients continue to suffer from chronic pain and ankle instability even after 3 to 9 months. Previously, we showed that the recombinant human amelogenin (rHAM⁺ ) induced regeneration of fully transected rat medial collateral ligament, a common proof-of-concept model. Our aim was to evaluate whether rHAM⁺ can regenerate torn ankle calcaneofibular ligament (CFL), an important component of the lateral ankle stabilizers. Right CFLs of Sabra rats were transected and treated with 0, 0.5, or 1 µg/µL rHAM⁺ dissolved in propylene glycol alginate (PGA). Results were compared with the normal group, without surgery. Healing was evaluated 12 weeks after treatment by mechanical testing (ratio between the right and left, untransected ligaments of the same rat), and histology including immunohistochemical staining of collagen I and S100. The mechanical properties, structure, and composition of transected ligaments treated with 0.5 μg/μL rHAM⁺ (experimental) were similar to untransected ligaments. PGA (control) treated ligaments were much weaker, lax, and unorganized compared with untransected ligaments. Treatment with 1 μg/μL rHAM⁺ was not as efficient as 0.5 μg/μL rHAM⁺ . Normal arrangement of collagen I fibers and of proprioceptive nerve endings, parallel to the direction of the force, was detected in ligaments treated with 0.5 μg/μL rHAM⁺ , and scattered arrangement, resembling scar tissue, in control ligaments. In conclusion, we showed that rHAM⁺ induced significant mechanical and structural regeneration of torn rat CFLs, which might be translated into treatment for grades 2 and 3 ankle sprain injuries.

Prolonged Rest, Long-Term Dynamic Balance, and Gait in a Mouse Ankle-Sprain Model

CONTEXT

Lateral ankle sprains (LASs) result in short- and long-term adaptations in the sensorimotor system that are thought to contribute to the development of chronic ankle instability and posttraumatic ankle osteoarthritis. Debate continues as to the appropriateness of rapid return to sport after LASs given the prevalence of long-term consequences.

OBJECTIVE

To examine the short- and long-term effects of prolonged rest, as a model of immobilization, on dynamic balance and gait outcomes after a severe LAS in a mouse model.

DESIGN

Controlled laboratory study.

SETTING

Research laboratory.

INTERVENTION(S)

At 7 weeks of age, 18 male mice (CBA/J) had their right anterior talofibular and calcaneofibular ligaments transected. Mice were then randomized to 1 of 3 groups representing when access to a running wheel postsurgery was gained: at 3 days, 1 week, and 2 weeks.

MAIN OUTCOME MEASURE(S)

Dynamic balance and spatial gait characteristics were quantified before surgery (baseline) and at 3 days and 1, 2, 4, 6, 12, 18, 24, 30, 36, 42, 48, and 54 weeks postinjury.

RESULTS

Relative to prolonged rest, resting for only 3 days resulted in worse dynamic balance during the later assessment points (42-54 weeks postinjury, P < .01). Mice that underwent a prolonged rest period of 2 weeks crossed the balance beam faster than the group that rested for only 3 days when averaged across all time points (P < .012). Spatial gait characteristics did not differ among the groups (P > .05).

CONCLUSIONS

Relative to 3 days of rest, prolonged rest (1 and 2 weeks) after a severe LAS in mice positively affected balance. The apparent benefit of prolonged rest was noted on both dynamic-balance outcomes and performance. Stride length was not altered by the duration of rest after a surgically induced severe LAS in mice. Future research is needed to determine if these results translate to a human model.

A 14-Day Recovery and Physical Activity Levels After an Ankle Sprain in Mice

CONTEXT

Research is needed to find ways of improving physical activity after a lateral ankle sprain.

OBJECTIVE

To investigate the effects of a prolonged rest period on lifelong activity after a surgically induced ankle sprain.

DESIGN

Controlled laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 18 male CBA/J mice (age at surgery = 7 weeks).

MAIN OUTCOME MEASURE(S)

We transected the anterior talofibular ligament and calcaneofibular ligament of the right hindlimb. Each mouse was placed in a separate cage and randomized into 1 of 3 groups of 6 mice each. A running wheel was placed in each cage at 3 days, 7 days, or 14 days after surgery. Physical activity was measured daily. Daily duration (ie, time spent on the wheel), distance, and running speed were examined using analysis of variance (group × age) with repeated measures at 15-week periods to approximate the first 3 quartiles of the lifespan.

RESULTS

From weeks 3 to 15 after surgery, we observed no differences in duration, distance, or running speed among groups (P > .05). From weeks 16 to 30, distance (F_2,14 = 0.57, P = .041) and running speed (F_2,14 = 0.93, P = .01) were greater in the 14-day group than in the 3- and 7-day groups. From weeks 31 to 45, duration (F_2,14 = 0.74, P = .02), distance (F_2,14 = 0.95, P = .009), and running speed (F_2,14 = 1.05, P = .007) were greater in the 14-day group than in the 3- and 7-day groups.

CONCLUSIONS

Our findings suggest that the longer recovery period of 14 days can increase activity levels throughout the lifespan after a severe ankle sprain. Rest after an ankle injury is critical to restoring physical activity levels across the lifespan. Rest and time away from exercise after an ankle sprain may be necessary to restore physical activity to normal, uninjured levels.

Lateral Ankle Sprain in a Mouse Model: Lifelong Sensorimotor Dysfunction

CONTEXT

  Ankle sprains are the most common orthopaedic injury that occurs during sport and physical activity. Many individuals who sprain their ankles develop chronic ankle instability (CAI), a condition characterized by recurrent injury, decreased physical activity, and decreased quality of life. These residual impairments are believed to persist for the remainder of the patient's life, in part due to the link between CAI and posttraumatic ankle osteoarthritis. However, this belief remains speculative due to the lack of long-term prospective investigations.

OBJECTIVE

  To use a mouse model of mild (MILD) and severe (SEVERE) ankle sprains to quantify balance and locomotor adaptations across the lifespan.

DESIGN

  Cohort study.

SETTING

  University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Fifty male mice (CBA/J) were randomly placed into a control (SHAM), MILD, or SEVERE group and housed individually.

INTERVENTION(S)

  The MILD group underwent surgical transection of a single right hind-limb lateral ankle ligament, and the SEVERE group had 2 of the lateral ligaments transected. The SHAM group underwent a sham surgery during which no lateral ligaments were transected.

MAIN OUTCOME MEASURE(S)

  After surgically inducing the ankle sprain, we measured balance and gait using a balance beam and footprint test before and every 6 weeks for 78 weeks.

RESULTS

  Age-related declines in balance but not stride length were exacerbated by an ankle sprain ( P < .001). Balance and stride lengths changed with age ( P < .001). Foot slips were worse in the SEVERE (4.32 ± 0.98) and MILD (3.53 ± 0.98) groups than in the SHAM group (2.16 ± 0.99; P < .001). Right-limb stride length was shorter in the SEVERE group (6.45 cm ± 0.41 cm) than in the SHAM group (6.87 cm ± 0.40 cm; P = .04).

CONCLUSIONS

  Transecting the lateral ligaments of a mouse hind foot resulted in lifelong sensorimotor dysfunction. Declines starting at 42 weeks postinjury may have represented the onset of posttraumatic osteoarthritis.

Acute Ankle Sprain in a Mouse Model: Changes in Knee-Joint Space

CONTEXT

  Ankle sprains remain the most common orthopaedic injury. Conducting long-term studies in humans is difficult and costly, so the long-term consequences of an ankle sprain are not entirely known.

OBJECTIVE

  To measure knee-joint space after a single surgically induced ankle sprain in mice.

DESIGN

  Randomized controlled trial.

SETTING

  University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Thirty male mice (CBA/2J) were randomly placed into 1 of 3 surgical groups: the transected calcaneofibular ligament (CFL) group, the transected anterior talofibular ligament/CFL group, or a sham treatment group. The right ankle was operated on in all mice.

MAIN OUTCOME MEASURE(S)

  Three days after surgery, all of the mice were individually housed in cages containing a solid-surface running wheel, and daily running-wheel measurements were recorded. Before surgery and every 6 weeks after surgery, a diagnostic ultrasound was used to measure medial and lateral knee-joint space in both hind limbs.

RESULTS

  Right medial (P = .003), right lateral (P = .002), left medial (P = .03), and left lateral (P = .002) knee-joint spaces decreased across the life span. The mice in the anterior talofibular ligament/CFL group had decreased right medial (P = .004) joint space compared with the sham and CFL groups starting at 24 weeks of age and continuing throughout the life span. No differences occurred in contralateral knee-joint degeneration among any of the groups.

CONCLUSIONS

  Based on current data, mice that sustained a surgically induced severe ankle sprain developed greater joint degeneration in the ipsilateral knee. Knee degeneration could result from accommodation to the laxity of the ankle or biomechanical alterations secondary to ankle instability. A single surgically induced ankle sprain could significantly affect knee-joint function.

Using mouse models to investigate the pathophysiology, treatment, and prevention of post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) is defined by its development after joint injury. Factors contributing to the risk of PTOA occurring, the rate of progression, and degree of associated disability in any individual, remain incompletely understood. What constitutes an "OA-inducing injury" is not defined. In line with advances in the traumatic brain injury field, we propose the scope of PTOA-inducing injuries be expanded to include not only those causing immediate structural damage and instability (Type I), but also those without initial instability/damage from moderate (Type II) or minor (Type III) loading severity. A review of the literature revealed this full spectrum of potential PTOA subtypes can be modeled in mice, with 27 Type I, 6 Type II, and 4 Type III models identified. Despite limitations due to cartilage anatomy, joint size, and bio-fluid availability, mice offer advantages as preclinical models to study PTOA, particularly genetically modified strains. Histopathology was the most common disease outcome, cartilage more frequently studied than bone or synovium, and meniscus and ligaments rarely evaluated. Other methods used to examine PTOA included gene expression, protein analysis, and imaging. Despite the major issues reported by patients being pain and biomechanical dysfunction, these were the least commonly measured outcomes in mouse models. Informative correlations of simultaneously measured disease outcomes in individual animals, was rarely done in any mouse PTOA model. This review has identified knowledge gaps that need to be addressed to increase understanding and improve prevention and management of PTOA. Preclinical mouse models play a critical role in these endeavors. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:424-439, 2017.

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.

Comparison of mouse and human ankles and establishment of mouse ankle osteoarthritis models by surgically-induced instability

OBJECTIVE

Prevalence of ankle osteoarthritis (OA) is lower than that of knee OA, however, the molecular mechanisms underlying the difference remain unrevealed. In the present study, we developed mouse ankle OA models for use as tools to investigate pathophysiology of ankle OA and molecular characteristics of ankle cartilage.

DESIGN

We anatomically and histologically examined ankle and knee joints of C57BL/6 mice, and compared them with human samples. We examined joints of 8-week-old and 25-month-old mice. For experimental models, we developed three different ankle OA models: a medial model, a lateral model, and a bilateral model, by resection of respective structures. OA severity was evaluated 8 weeks after the surgery by safranin O staining, and cartilage degradation in the medial model was sequentially examined.

RESULTS

Anatomical and histological features of human and mouse ankle joints were comparable. Additionally, the mouse ankle joint was more resistant to cartilage degeneration with aging than the mouse knee joint. In the medial model, the tibiotalar joint was markedly affected while the subtalar joint was less degenerated. In the lateral model, the subtalar joint was mainly affected while the tibiotalar joint was less altered. In the bilateral model, both joints were markedly degenerated. In the time course of the medial model, TdT-mediated dUTP nick end labeling (TUNEL) staining and Adamts5 expression were enhanced at early and middle stages, while Mmp13 expression was gradually increased during the OA development.

CONCLUSION

Since human and mouse ankles are comparable, the present models will contribute to ankle OA pathophysiology and general cartilage research in future.

Altered left ventricular performance in aging physically active mice with an ankle sprain injury

We assessed the impact of differing physical activity levels throughout the lifespan, using a musculoskeletal injury model, on the age-related changes in left ventricular (LV) parameters in active mice. Forty male mice (CBA/J) were randomly placed into one of three running wheel groups (transected CFL group, transected ATFL/CFL group, SHAM group) or a SHAM Sedentary group (SHAMSED). Before surgery and every 6 weeks after surgery, LV parameters were measured under 2.5 % isoflurane inhalation. Group effects for daily distance run was significantly greater for the SHAM and lesser for the ATLF/CFL mice (p = 0.013) with distance run decreasing with age for all mice (p < 0.0001). Beginning at 6 months of age, interaction (group × age) was noted with LV posterior wall thickness-to-radius ratios (h/r) where h/r increased with age in the ATFL/CFL and SHAMSED mice while the SHAM and CFL mice exhibited decreased h/r with age (p = 0.0002). Passive filling velocity (E wave) was significantly greater in the SHAM mice and lowest for the ATFL/CFL and SHAMSED mice (p < 0.0001) beginning at 9 months of age. Active filling velocity (A wave) was not different between groups (p = 0.10). Passive-to-active filling velocity ratio (E/A ratio) was different between groups (p < 0.0001), with higher ratios for the SHAM mice and lower ratios for the ATFL/CFL and SHAMSED mice in response to physical activity beginning at 9 months of age. Passive-to-active filling velocity ratio decreased with age (p < 0.0001). Regular physical activity throughout the lifespan improved LV structure, passive filling velocity, and E/A ratio by 6 to 9 months of age and attenuated any negative alterations throughout the second half of life. The diastolic filling differences were found to be significantly related to the amount of activity performed by 9 months and at the end of the lifespan.

Physical Activity Levels in College Students With Chronic Ankle Instability

CONTEXT

Ankle sprains are the most common orthopaedic pathologic condition, and more concerning is the high percentage of persons who develop chronic ankle instability (CAI). Researchers have reported that patients with CAI are restricted occupationally, have more functional limitations, and have a poorer health-related quality of life. We do not know if these limitations decrease physical activity levels.

OBJECTIVE

To assess total weekly steps taken between persons with CAI and persons with healthy ankles.

DESIGN

Case-control study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 participants with unilateral CAI (9 men, 11 women; age = 21.2 ± 1.9 years, height = 174.3 ± 6.9 cm, mass = 71.9 ± 11.7 kg) and 20 healthy participants (9 men, 11 women; age = 20.4 ± 2.1 years, height = 172.1 ± 5.5 cm, mass = 73.1 ± 13.4 kg) volunteered.

MAIN OUTCOME MEASURE(S)

We provided all participants with a pedometer and instructed them to wear it every day for 7 days and to complete a daily step log. They also completed the Foot and Ankle Ability Measure (FAAM), the FAAM Sport version, and the International Physical Activity Questionnaire. A 2-way analysis of variance (group × sex) was used to determine if differences existed in the total number of weekly steps, ankle laxity, and answers on the International Physical Activity Questionnaire between groups and between sexes.

RESULTS

We found no group × sex interaction for step count (F range = 0.439-2.108, P = .08). A main effect for group was observed (F(1,38) = 10.45, P = .04). The CAI group took fewer steps than the healthy group (P = .04). The average daily step count was 6694.47 ± 1603.35 for the CAI group and 8831.01 ± 1290.01 for the healthy group. The CAI group also scored lower on the FAAM (P = .01) and the FAAM Sport version (P = .01).

CONCLUSIONS

The decreased step count that the participants with CAI demonstrated is concerning. This decreased physical activity may be secondary to the functional limitations reported. If this decrease in physical activity level continues for an extended period, CAI may potentially be a substantial health risk if not treated appropriately.