Preoperative MRI is a reliable and valid decision making tool for the choice of surgical stabilization technique in patients with chronic lateral ankle instability
The anterior talofibular ligament (ATFL) is the most frequently affected ligament in chronic lateral ankle instability. When surgery is indicated, the choice of technique is performed intraoperatively according to the aspect of the residual ATFL under arthroscopy. In our department, the technique used is either the arthroscopic Brostrom Gould procedure repair if the ligament is thickened or disinserted at the fibula attachment, or an anatomical reconstruction of the anterior talofibular and calcaneofibular ligaments with a gracilis autograft if ATFL is absent or thin. The purpose of this study was to assess the reliability and validity of preoperative MRI for surgical decision making in chronic lateral ankle instability.
Material And Methods
This single-center prospective study included all patients who underwent an arthroscopic ankle stabilization between 2013 and 2016. The study complied with the recommendations of the group STARD (Standards for Reporting of Diagnostic Accuracy). Preoperative MRI evaluation of ATFL was performed in axial T2-weighted images, twice, by 2 independent observers who where blinded to the arthroscopic assessment. The ATFL was noted (1)absent, (2)thin (diameter <1mm), (3)normal diameter (1-3.2mm) but with wavy or curved contours, elongation or avulsion, and (4)thickened (diameter >3.2mm) with or without high signal intensity within the ligament. Arthroscopy assessment, used as the gold standard in this study, was carried out by a single senior surgeon. The primary endpoint was the ATFL aspect in two categories: (1)thin or absent/(2)avulsed or thickened. The intra and inter-observer agreement was assessed by the kappa coefficient (k). The diagnostic performance parameters of preoperative MRI were calculated relative to arthroscopy: sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative (NPV) and the percentage of correctly classified patients.
Twenty two patients were included in this study, 15 men/7 women with a mean age of 30.3±9.5 years. An anatomical ligament repair was performed in 14 patients (63.6%), and 8 patients (36.4%) underwent a ligamentoplasty with a gracilis autograft. The intra-observer reproducibility of MRI analysis was substantial (k=0.75 and 0.68) and inter-observer reproducibility was moderate (k=0.55) to almost perfect (k=0.87). In comparison with arthroscopy, the agreement was substantial and significant (k=0.70 and 0.80). Performance parameters of preoperative MRI were good for the two evaluators: Se=85.7 to 87.5%, Sp=86.7 to 92.9%, PPV=75 to 87.5%, NPV=92.9% and percentage of patients correctly classified 86.4 to 90.9%.
Preoperative MRI is a reliable and valid decision making tool for the choice of surgical stabilization technique in patients with chronic lateral ankle instability.