SLR - June 2017 - Wyatt I. Wiedenfeld
Reference: Harnroongroj T, Cheuckpaiwong B. Is the Arthroscopic Transillumination Test Effective in Localizing the Superficial Peroneal Nerve? Arthroscop. 2017 Mar; 33(3): 647–650.Reviewed By: Wyatt I. Wiedenfeld, DPM
Residency Program: Providence-Providence Park Hospital, Southfield, MI
Podiatric Relevance: Over the last decade, ankle arthroscopy has become a very common procedure to surgically address a large variety of pathology, including synovitis, impingement, talar dome lesions and even for diagnostic purposes. Despite its popularity, ankle arthroscopy is not without its complications, one of its most common being injury to the superficial peroneal nerve (SPN) during the creation of the anterior lateral portal. In an attempt to prevent injury to the nerve, the most basic and popular technique includes preoperatively marking the location of the nerve by maximally plantarflexing and inverting the ankle while plantarflexing the fourth digit. The disadvantage of this technique is the difficulty and effectiveness in visualizing the nerve in obese patients. This study looks to examine the reliability of a different technique that utilizes intraoperative transillumination via the arthroscope from the medial portal.
Methods: A level II prospective diagnostic study was performed on patients undergoing ankle arthroscopy at a single institution from 2013 to 2016. Inclusion criteria included patients who had a visible SPN preoperatively. Exclusion criteria included patients with significant deformity at the ankle or tibia and those with previous anterior ankle surgeries. Patients in whom the SPN could not be visualized by plantarflexing and inverting the ankle were excluded because this served as a landmark for transillumination. Operative technique included supine position with 45 degrees hip flexion and 90 degrees knee flexion with ankle distractor. Standard anterior medial portal was created medial to the tibialis anterior tendon at the level of the ankle joint. Transillumination was performed with a 4.0 mm arthroscope with the room lights turned off while directing laterally at the marked location of the SPN. The result was considered positive when the SPN could be visualized. The test was performed by two surgeons who were blinded from each other’s results for interobserver reliability. Data was analyzed as mean, standard deviation and percentage.
Results: There was a total of 124 arthroscopic ankle patients. Only 53 patients (42.7 percent) had a visible SPN. Average BMI of the 53 included patients was 25.8. Intraoperatively, the transillumination test was positive 0 of the total 53 arthroscopic ankle patients. In all cases, both surgeons agreed that the SPN was not visible.
Conclusion: The results of this study showed that the transillumination test could not identify the SPN in any of the 53 patients who underwent ankle arthroscopy and met the inclusion criteria. The authors concluded that the transillumination test has no value for showing the SPN. As discussed, the SPN at the level of the ankle is mostly sensory nerves and poorly myelinated, resulting in a water content not much different from surrounding tissue making transillumination difficult. Despite vascular structures being easily visualized, these do not accompany the SPN at this level. I believe this study to show the lack of reliability with either of the most popular techniques to identify the SPN, which only further stresses the importance of proper portal incision orientation and atraumatic dissection techniques to minimize the chance of complications.