Comparison between Magnification Techniques and Direct Vision in Thyroid Surgery: A Systematic Review and Meta-Analysis

Background and Objectives: The most common complications after conventional thyroid surgery in adult patients are recurrent laryngeal nerve (RLN) injury and hypocalcemia. Magnification techniques (surgical loupes or surgical microscope) are used for identification of RLN and parathyroid glands to diminish these complications although more evidence is necessary to assess their safety and efficacy in comparison with direct vision. Methods and Materials: Electronic databases (Pubmed, Cochrane Library, Scopus) as well as gray literature sources were searched for randomized controlled trials (RCTs) comparing the frequency of transient/permanent RLN injury and hypocalcemia after thyroid surgery by using magnification techniques and direct vision for identification of RLN and parathyroid glands until October 17, 2019. The main outcomes were transient/permanent RLN injury and hypocalcemia. For all outcomes, 95% confidence intervals (95% CI) were used. Statistical analysis was performed with RevMan 5.3. Results: Systematic review and meta-analysis included 3 RCTs with 437 patients overall. Magnification techniques did not significantly affect the risk of occurrence of transient RLN injury (OR = 0.38, 95% CI (0.11−1.35), I2 = 0%) and transient hypocalcemia (OR = 0.31, 95% CI (0.09−1.09), I2 = 23%) compared with direct vision. Included RCTs demonstrated only two patients with permanent hypocalcemia and another one with permanent RLN injury, who belonged to the direct vision group. Conclusion: The use of magnification techniques for identification of RLN and parathyroid glands seems to be as safe as direct vision. However, they do not decrease the risk of RLN injury and transient hypocalcemia after thyroid surgery compared with direct vision. Finally, further prospective research should be conducted as the sample among the studies was small.