Definition of learning curve for thyroidectomy: systematic review on the different approaches

Background: Thyroidectomy is one of the most common surgical procedures carried out worldwide and it has evolved in recent years with alternative approaches. With the advent of minimally invasive techniques, the learning curve (LC) concept has become a fundamental "dogma". Methods: A literature search, according to the PRISMA guidelines, was performed via PubMed (MEDLINE), Scopus, Cochrane Library, EMBASE, and Web of Science. Only studies assessing the learning process to thyroidectomy (including hemi- and total thyroidectomy), reporting a minimum of 30 procedures and describing clearly the minimum number of performances required to achieve proficiency and the main evaluation items used to establish it, were included. Conventional, endoscopic and robotic approaches were separately analyzed. Only English-language studies were considered. Results: Forty-five relevant studies were selected for the analysis [respectively 16 concerning robotic thyroidectomy (RT), 22 endoscopic thyroidectomy (ET), 6 mini-invasive video assisted thyroidectomy (MIVAT), 1 conventional thyroidectomy (CT)]. The number of procedures required for a single surgeon to achieve competence and the parameters used to define surgical proficiency were fully investigated for each individual technique. Conclusions: Our research shows how the current literature lacks an objective definition of the LC concept. The heterogeneity of analysis methodologies and parameters evaluated, the various surgical techniques and training background of single surgeons, make it impossible to draw univocal results. Future studies should consider confounding factors and establish criteria that should be consensually recognized in the assessment of surgical performances and skills.