BACKGROUND: Although the Nirschl technique was introduced approximately 40 years ago, only limited information is available about the long-term results, especially concerning extensor power changes after surgery. The purpose of this study was to investigate long-term clinical results of surgical treatment of lateral epicondylitis using the modified Nirschl technique. The main outcome variable was muscle strength for wrist extension because the extensor origin was not reattached after removal of the degenerative extensor tendon. METHODS: Data from 99 patients who underwent surgical lateral epicondylitis treatment between 2007 to 2012 were included in the study. The mean follow-up period was 8.5 years (5 to 10, ± 1.1 years) and the mean age at surgery was 44.8 years (32 to 70, ± 9.8 years). The surgeries were performed using the modified Nirschl method and did not include extensor origin reattachment. Outcome measurements included the Visual Analogue Scale (VAS) score, Disabilities of the Arm, Shoulder and Hand (DASH) score, the MAYO elbow performance score, and Nirschl and Pettrone's grades. Wrist extension and grip strength were analyzed using a digital handgrip dynamometer (microFET2TM system) and JAMA hand dynamometer. RESULTS: Mean time required to return to work was 2.4 months after surgery. At the last follow-up after surgery, the mean VAS score had significantly improved, from 4.9 to 1.1. Mean MAYO elbow performance scores significantly improved, from 64 to 90, and mean DASH scores improved from 50 to 13. The Nirschl and Pettrone's grades were 80% rated as 'excellent' and 16% rated as 'good'. After adjusting for power differences between the dominant and non-dominant arms, the difference between wrist extensor power of the operated elbow and the non-operated opposite elbow at the final follow-up was not statistically significant. No patients complained about wrist extension weakness. CONCLUSION: Although reattachment of the extensor origin was not performed during the modified Nirschl surgical technique, there was no significant weakness in wrist extension power and the long-term follow-up revealed favorable clinical results. LEVEL OF EVIDENCE: Level IV (case series). Retrospective study.