Comparative Post-operative Outcomes between Positive and Negative Electromyography (EMG) in Patient with Tunnel Syndrome: A Retrospective Study
Authors: Rungprai Chamnanni , Hempongphan Tanarat , Sripanich Yantarat , Pongpinyopap Warongporn , Boonma Pisit 
Published: November 2020

Category: Other Introduction/Purpose: Tarsal tunnel syndrome can be established using combination of physical examination and electrodiagnostic study including tenderness along tibial nerve in tarsal tunnel area, Tinel sign positive, and positive EMG. However, it has been reported that the sensitivity of the electrodiagnostic study is only 52% for diagnosis of tarsal tunnel syndrome. Therefore, although EMG is negative, some surgeons prefer to make a diagnosis base on physical examination. Conservative treatment is the first line of treatment and when this fails, surgical treatment is indicated. The purpose of this study was to compare post-operative outcomes following tarsal tunnel release in patients who had tarsal tunnel syndrome with positive and negative electrodiagnostic study. Methods: The retrospective chart review of 34 consecutive patients who had underwent tarsal tunnel release between 2015 and 2019 were enrolled in this study. The patients were classified into 2 groups based on results of electrodiagnostic study (negative EMG 15 patients and positive EMG 18 patients). All patients had been treated with conservative treatment for at least 6 months including modified inserted and shoe wear, activities modifications, NSAIDs, and gabapentin. The primary outcome was pain level using Visual Analogue Scale (VAS) while the secondary outcomes were SF-36, FAAM, recovery times (time to return to ADL, work, and sports), and complications. A paired sample t-test was used to assess statistical differences between pre- and post- operative functional outcomes (VAS, SF-36, and FAAM) in the same group of both negative and positive EMG while an independent t-test was used to compare functional outcomes (VAS, SF-36, and FAAM) between the negative and positive EMG. Results: There were 33 patients (15 male and 18 female) with mean age of 49.2 years (range, 25-71 years), mean BMI of 24.7 kg/m2 (range, 17.6-33.2 kg/m2), and mean follow-up of 17.9 months (range, 12-36 months). The mean duration of symptom before the surgery was 8.7 months and 10.2 months for EMG negative and positive respectively. Both groups demonstrated significant improvement of all functional outcomes (FAAM, SF-36, and VAS (p<0.001 all)) compared to pre-operative status; however, there was no significant difference between the two groups, (p>0.05 all). The recovery time were to return to daily activities (3.5 vs 3.6 weeks), time to return to work (5.4 vs 5.6 weeks), and time to return to sport (16.4 vs 17.1 weeks). There were no complications in both groups Conclusion: Tarsal tunnel release demonstrated significantly improvement of functional outcomes in both negative and positive electrodiagnostic study in patients as measured with VAS, SF-36, and FAAM. However, negative EMG did not demonstrate negative impact on functional outcomes after tarsal tunnel release. When clinical and physical examination suspects tarsal tunnel syndrome, tarsal tunnel release should be considered even thought there is negative on electrodiagnostic study.