Pre-operative MRI for Antero-lateral Ankle Impingement - Where is Basset`s Ligament?

Introduction: Antero-lateral impingement syndrome is described as pain and limitation of dorsiflexion. It is often seen in active patients after moderate to severe ankle sprain. A common cause is a partial or complete tear of the distal part of anterior inferior talofibular ligament, also known as Bassett`s ligament. The hypertrophied scarred ligament, surrounded by synovial tissue, protrudes to antero-lateral corner of the ankle and impinges in dorsiflexion. This ligament was first described and classified in cadaver models, and later found on MRI in several studies. Today, the surgical treatment of choice is arthroscopic resection.

Method: We have retrospectively examined the preoperative MRI of patients who underwent arthroscopy for antero-lateral pain, with intraoperative finding of impinging Bassett`s ligament. All arthroscopies were performed by a single surgeon and all MRI reviews were conducted by musculoskeletal radiologist.

Results: Of 53 ankle arthroscopies preformed during 2016, 15 patients had a finding of impinging Bassett`s ligament and their preoperative MRI studies were available. The average age was 33, male:female ratio of 8:7 . None of the 15 patients had a finding of Bassett`s ligament on the initial MRI report by a radiologist. Two of the MRI studies retrospectively reviewed were suggestive of impinging Bassett`s ligament.

Conclusions: Antero-lateral impingement syndrome is a common cause of pain and is easily recognized by arthroscopy. Preoperative and also retrospective review of MRI examinations couldn`t clearly detect the impingement and it cause. MRI routine includes sagittal, coronal and axial planes, without the use of oblique view which is the preferred view for visualization of syndesmotic ligaments, and might assist in detecting the cause for impingement. It seems that clinical examination is still the most sensitive way to diagnose the impingement. Further study is required to evaluate and improve the value of MRI for diagnosis of antero-lateral impingement syndrome.