Arthroscopic characterization of syndesmotic instability in the coronal plane: Exactly what measurement matters?

Value of arthroscopy in the management of acute lesions of the distal tibiofibular joint

PURPOSE

Managing the distal tibiofibular (DTF) joint remains a challenge despite recent developments. Ankle arthroscopy is emerging as a diagnostic and therapeutic means. Our study aimed to compare preoperative imaging data and arthroscopic data, with the hypothesis that imaging alone is insufficient to evaluate acute laxity, and with arthroscopy as the reference examination.

METHODS

All patients treated in 2023 in our department for an acute isolated DTF lesion were included prospectively. Preoperative radiographic and MRI imaging were compared with arthroscopic data.

RESULTS

Ten patients were treated. For five patients, the instability was doubtful after carrying out an appropriate imaging assessment (X-rays of both ankles, MRI). For four of these five patients, instability was confirmed by arthroscopy. Arthroscopy was useful for suturing the anterior bundle of the DTF joint for two patients and allowed for verifying the reduction in the sagittal and coronal planes for two patients. No complications were detected.

CONCLUSIONS

Arthroscopy in isolated acute DTF lesions seems to provide a diagnostic and therapeutic advantage. Its use may allow for exhaustive assessment and complete repair of lesions. It must be offered as soon as possible; a delay in specialized imaging may delay therapeutic care.

Volume measurements on weightbearing computed tomography can detect subtle syndesmotic instability

While weightbearing computed tomography (WBCT) allows three-dimensional (3D) visualization of the distal syndesmosis, image interpretation has largely relied on one-dimensional (1D) distance and, more recently, two-dimensional (2D) area measurements. This study aimed to (1) determine the sensitivity and specificity of 2D area and 3D volume WBCT measurements towards detecting subtle syndesmotic instability, (2) evaluate whether the patterns of changes in the 3D shape of the syndesmosis can be attributed to the type of ligament injury. A total of 24 patients with unilateral subtle syndesmotic instability and 24 individuals with uninjured ankles (controls) with bilateral ankle WBCT were assessed retrospectively. First, 2D areas at 0, 1, 3, 5, and 10 cm, and 3D volumes at 1, 3, 5, and 10 cm above the tibial plafond were measured bilaterally. Secondly, the 3D model of the distal tibiofibular space was created based on WBCT in a subset of 8 out of 24 patients in whom the type of ligament injury was recognized via magnetic resonance imaging. The 3D model of the injured side was superimposed on the uninjured contralateral side to visualize the pattern of changes in different planes. Volume measurement up to 5 cm above the tibial plafond showed the lowest p-value (<0.001 vs. other methods), higher sensitivity (95.8%, 95% confidence interval [CI]: 87.8-100), and specificity (83.3%, 95% CI: 68.4-98.2) for detection of syndesmotic instability. No specific pattern of changes in the 3D shape could be attributed to a type of ligament rupture. We suggest 3D volume measurements, best measured up to 5 cm proximal to the plafond, as a promising means of diagnosing syndesmotic instability, particularly for subtle cases that are hard to detect. Clinical significance: The ability to compare the ankle joints bilaterally in a 3D manner under physiologic weight provided by weightbearing CT has led to a more accurate diagnostic method. Using volumetric measurement up to 5 cm above the tibial plafond showed higher sensitivity and specificity for recognizing an unstable syndesmosis, especially in subtle cases. However, our preliminary investigations showed that the pattern of 3D alterations in the distal tibiofibular joint space based on WBCT images does not indicate the type of syndesmotic ligamentous injury. Our results can also help image viewing programs to improve their measurement tools to facilitate 3D measurement for the syndesmosis as well as other conditions that may benefit from 3D evaluation of the clinical images.