Endoscopic Flexor Hallucis Longus Transfer for Achilles Noninsertional Tendinopathy: Description of Surgical Technique and Functional Outcomes.

. The transfer of the flexor hallucis longus (FHL) tendon is an established treatment for replacing a dysfunctional Achilles tendon. . (1) Describe a new technique for endoscopic FHL transfer for noninsertional Achilles tendinopathy and (2) describe the functional outcomes and complications after endoscopic and open FHL transfer. . Retrospective study of patients who underwent open or endoscopic FHL transfer between 2014 and 2016. The American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot scale was used preoperatively and postoperatively to measure the functional results. . We included 18 endoscopic FHL transfers and 24 open FHL transfers. The mean age of endoscopic and open procedures was 47.5 years (range 25-77 years) and 61.2 years (range 43-72 years), respectively. An improvement on the average AOFAS of 52.8% (31.9 points) was observed in the endoscopy group during the follow-up from the baseline. The mean improvement in AOFAS score for the open group was 41.4% (24.5 points). Four and 7 cases reported complications in the endoscopy and open FHL transfer groups, respectively. . While both procedures were effective in treating noninsertional Achilles tendinopathy, the described arthroscopic treatment led to a greater improvement in the AOFAS score and is slightly less prone to lasting complications. Level IV: Case series.