In vivo analysis of ankle joint kinematics and ligament deformation of chronic ankle instability patients during level walking.

Introduction: Chronic ankle instability (CAI) carries a high risk of progression to talar osteochondral lesions and post-traumatic osteoarthritis. It has been clinically hypothesized the progression is associated with abnormal joint motion and ligament elongation, but there is a lack of scientific evidence. Methods: A total of 12 patients with CAI were assessed during level walking with the use of dynamic biplane radiography (DBR) which can reproduce the in vivo positions of each bone. We evaluated the uninjured and CAI side of the tibiotalar and subtalar joint for three-dimensional kinematics differences. Elongation of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL) were also calculated bilaterally. Results: For patients with CAI, the dorsiflexion of the tibiotalar joint had reduced (21.73° ± 3.90° to 17.21° ± 4.35°), displacement of the talus increased (2.54 ± 0.64 mm to 3.12 ± 0.55 mm), and the inversion of subtalar joint increased (8.09° ± 2.21° to 11.80° ± 3.41°). Mean ATFL elongation was inversely related to mean dorsiflexion angle (CAI: rho = -0.82, P < 0.001; Control: rho = -0.92, P < 0.001), mean ATFL elongation was related to mean anterior translation (CAI: rho = 0.82, P < 0.001; Control: rho = 0.92, P < 0.001), mean CFL elongation was related to mean dorsiflexion angle (CAI: rho = 0.84, P < 0.001; Control: rho = 0.70, P < 0.001), and mean CFL elongation was inversely related to mean anterior translation (CAI: rho = -0.83, P < 0.001; Control: rho = -0.71, P < 0.001). Furthermore, ATFL elongation was significantly (CAI: rho = -0.82, P < 0.001; Control: rho = -0.78, P < 0.001) inversely correlated with CFL elongation. Discussion: Patients with CAI have significant changes in joint kinematics relative to the contralateral side. Throughout the stance phase of walking, ATFL increases in length during plantarflexion and talar anterior translation whereas the elongation trend of CFL was the opposite. This understanding can inform the development of targeted therapeutic exercises aimed at balancing ligament tension during different phases of gait. The interrelationship between two ligaments is that when one ligament shortens, the other lengthens. The occurrence of CAI didn't change this trend. Surgeons might consider positioning the ankle in a neutral sagittal plane to ensure optimal outcomes during ATFL and CFL repair.

The Biomechanical Influence of Defected Cartilage on the Progression of Osteochondral Lesions of the Talus: A Three-dimensional Finite Element Analysis.

OBJECTIVES: Osteochondral lesions of the talus (OLTs) are common injuries in the general population. Abnormal mechanical conditions applied to defected cartilage are believed to be the culprits to deteriorating OLTs. This study aims to investigate the biomechanical effects of defect size of talar cartilage on OLTs during ankle movements. METHODS: A finite element model of the ankle joint was created based on the computed tomography images of a healthy male volunteer. Different defect sizes (S = 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, and 2.0 cm2 ) of talar cartilage were modeled to simulate the progression of OLTs. Mechanical moments were applied to the model to generate different ankle movements, including dorsiflexion, plantarflexion, inversion, and eversion. The effects of varying defect sizes on peak stress and its location were evaluated. RESULTS: The maximum stress on the talar cartilage increased as the area of the defect enlarged. Additionally, as the defect size of OLTs increased, the areas with peak stress on talar cartilage tended to move closer to where the injury was located. High stresses were present in the medial and lateral areas of the talus at the neutral position of the ankle joint. The concentrated stresses were mainly located in the anterior and posterior defect areas. The peak stress in the medial region was higher than on the lateral side. The order of peak stress from highest to lowest was dorsiflexion, internal rotation, inversion, external rotation, plantar flexion, and eversion. CONCLUSIONS: Osteochondral defect size and ankle joint movements significantly modulate the biomechanical features of the articular cartilage in osteochondral lesions of the talus. The progression of osteochondral lesions in a talus deteriorates the biomechanical well-being of the bone tissues of the talus.

Neurological deterioration as a result of improper neck position detected by intraoperative neurophysiological monitoring in a cervical stenosis patient: A case report.

RATIONALE: Intraoperative neurophysiological monitoring (IONM) is widely used in spinal surgeries to prevent iatrogenic spinal cord injury (SCI). Most surgeons focus on avoiding neurological compromise intraoperatively, while ignoring the possibility of nerve damage preoperatively, such as neck positioning. Thus, this study aims to report a case with transient neurological deterioration due to improper neck position detected by IONM during cervical surgery. PATIENT CONCERNS: A 63-year-old male patient had been suffering from hypoesthesia of the upper and lower extremities for three years. DIAGNOSES: Severe cervical stenosis (C5-C7) and cervical ossification of a posterior longitudinal ligament. INTERVENTIONS: The cervical stenosis patient underwent an anterior cervical corpectomy decompression and fusion (ACDF) surgery with the assistance of IONM. When the lesion segment was exposed, the SSEP and MEP suddenly elicited difficulty indicating that the patient may have developed SCI. All the technical causes of IONM events were eliminated, and the surgeon suspended operation immediately and suspected that the IONM alerts were caused by cervical SCI due to the improper position of the neck. Subsequently, the surgeon repositioned the neck of the patient by using a thinner shoulders pad. OUTCOMES: At the end of the operation, the MEP and SSEP signals gradually returned to 75% and 80% of the baseline, respectively. Postoperatively, the muscle strength of bilateral biceps decreased from grade IV to grade III. Besides, the sensory disturbance of both upper extremities aggravated. However, the muscle power and hypoesthesia were significantly improved after three months of neurotrophic therapy and rehabilitation training, and no complications of nerve injury were found at the last follow-up visit. LESSONS: IONM, consisting of SSEP and MEP, should be applied throughout ACDF surgery from the neck positioning to suture incisions. Besides, in the ward 1to 2 days before operation, it is necessary for conscious patients with severe cervical stenosis to simulate the intraoperative neck position. If the conscious patients present signs of nerve damage, they can adjust the neck position immediately until the neurological symptoms relieve. Therefore, intraoperatively, the unconscious patient can be placed in a neck position that was confirmed preoperatively to prevent SCI.