An alternative injection technique for performing MR ankle arthrography: the lateral mortise approach

This study evaluates whether the recently described lateral mortise (LM) approach to therapeutic ankle injections can also be used to inject the ankle prior to magnetic resonance arthrography (MRA) without impairing the evaluation of the anterior talofibular ligament (ATFL).

An IRB-approved, retrospective review of ankle MRAs performed using the LM approach between April 2009 and April 2011 was conducted. The MRAs were independently evaluated by three musculoskeletal radiologists for: ATFL assessment (well assessed, limited or unable to assess), amount of fluid in the anterolateral soft tissues (none to large), and capsular distention (underdistended to overdistended). Patient age, gender, fluoroscopy time, injection location, degree of ankle arthritis, and ankle joint narrowing on radiographs were recorded. Statistical analysis was performed using exact binomial confidence limits.

Fifteen MRAs were successfully performed on 13 patients (mean age: 27 years, 11 male, 2 female). Mean fluoroscopic time was 39 s (range 9–108) and mean volume injected was 7 mL (range 5–9 mL). The ATFL was well assessed on all MRAs. A moderate to large amount of fluid was noted in the anterolateral soft tissues on 5 out of 15 MRAs. No ankle joints were underdistended, but 3 out of 15 were overdistended.

Since the ATFL is inferior to the location used for the LM injection, the interpretation of the ankle MRA, specifically ATFL evaluation, was not compromised in any patient. Therefore, the LM approach can be used as an alternative to the anteromedial approach for ankle MRA without sacrificing diagnostic quality.