The biomechanical influence of tibio-talar containment on stability of the ankle joint

Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively, little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar surface and the tibial coverage of the talus (sector α) were measured on a DICOM/PACS system in 52 patients with CAI and an age- and sex-matched control group. The talar radius was found to be larger in patients with CAI (21.2 ± 2.4 mm) than in the control group (17.7 ± 1.9 mm; P < 0.0001). The tibio-talar sector was smaller in patients with CAI (80° ± 5.1°) than in the control group (88.4° ± 7.2°; P < 0.0001). The aim of this study is to analyse the biomechanical influence of the clinical data on stability of the ankle joint. A two-dimensional model of the tibio-talar joint in the sagittal plane was developed. The joint configuration was described by the tibio-talar sector (α) and the radius (r) of the talus. The force (F = F BW tan α/2) and energy (E = F BW r [1 − cos α/2]) to dislocate the talus out of the tibial plafond were deduced. Ankle stability is a function of the tibio-talar sector: the force necessary to dislocate the joint is decreasing with a smaller sector. The clinical data show that the force needed to dislocate the ankle of CAI patients was 14% weaker than the one needed in the case of healthy subjects (P < 0.0001). The energy to dislocate the ankle depends both on the sector and the radius. The clinical data do not show a significant difference between the energy needed to dislocate the joint of CAI patients and the one of healthy subjects. This is because there is a correlation of a small sector and a large radius for CAI ankles. CAI is associated with an unstable osseous joint configuration, which is characterized by a larger radius of the talus and a smaller tibio-talar sector. The findings of the biomechanical model explain the clinical observations and demonstrate how stability of the ankle joint is influenced by the osseous configuration. Surgical ankle ligament stabilization might be more recommended in patients with an unstable osseous configuration as such patients have a disposition for recurrent sprains. Removing anterior osteophytes for anterior impingement should be done carefully in CAI patients because this would decrease the tibial coverage of the talus and thus dispose the talus to dislocate anteriorly. People who have an unstable ankle configuration and who nevertheless engage in activities with high risk of ankle sprains could be asked to wear ankle protecting sports equipment

Surgical treatment paradigms of ankle lateral instability, osteochondral defects and impingement

Ankle sprain is amongst the most frequent musculoskeletal injuries, particularly during sports activities. Chronic ankle instability (CAI) resulting from an ankle sprain might have severe long-lasting consequences on the ankle joint. Despite the fact that most patients will respond favourably to appropriate conservative treatment, around 20% will develop symptomatic CAI with sense of giving away and recurrent sprains leading to functional impairment. “Classical” surgical repair by Brostrom-like surgery in one of its many modifications has achieved good results over the years. Recently, major advances in surgical techniques have enabled arthroscopic repair of ankle instability with favourable outcome while also enabling the treatment of other concomitant lesions: loose bodies, osteochondral defects (OCDs) or ankle impingement. Moreover, when the tissue remnant does not permit a repair technique, anatomic reconstruction by means of using a free graft has been developed. In many cases, OCDs occur as a consequence of CAI. However, traumatic and non-traumatic aetiologies have been described. There is no evidence favouring any surgical treatment over another concerning OCDs. Considering lower cost and limited aggression, microfracture is still the most frequent surgical approach. Herein, the authors describe their algorithm in the treatment of these conditions. Similarly, anterior or posterior impingement might be linked with CAI. These are clinical syndromes based on clinical diagnosis which are currently managed arthroscopically upon failure of conservative treatment