en Gamma Knife Radiosurgery Research <p style="text-align: justify;">Background & Aim: The purpose of this study was to evaluate and compare the pain of patients with spondylolisthesis who had undergone either of the surgery techniques: posterolateral fusion (PLF) or posterior lumbar interbody fusion (PLIF). Methods & Materials/Patients: In a prospective observational study, 102 surgical candidates with low grade degenerative and isthmic spondylolisthesis were enrolled from 2012 to 2014. The observed patients were into two groups: PLF and PLIF. Assessing of pain has been done by a questionnaire using Visual Analogue Scale (VAS) scores. The questionnaire was completed by all patients before surgery, the day after surgery, after six months and after one year. Results: There were no statistically significant differences in terms of age and sex distribution, type of spondylolisthesis and pre-operation pain between groups (p>0.05). Comparison of the mean VAS scores of two groups over the whole study period showed a significant statistical difference (p-value<0.05), although comparison of VAS at three points in time showed a mixed result. VAS scores showed no significant differences between two groups before surgery, the day after surgery and one year after surgery (p>0.05), but the difference of mean VAS scores between groups 6 months after surgery was statistically significant (p<0.05). Analyzing the course of VAS scores over the study period showed a descending pattern for either of the groups (p<0.0001). Conclusion: Both surgical fusion techniques (PLF & PLIF) showed to be effective in treating low grade degenerative and isthmic spondylolisthesis, but PLIF was related to better outcome with respect to pain control.</p> Spondylolisthesis, Fusion, Pain, Isthmic, Degenerative 22 26 http://irjns.org/browse.php?a_code=A-10-100-21&slc_lang=en&sid=1 Babak Alijani بابک علیجانی 10031947532846002984 10031947532846002984 No MD, Assistant Professor of Neurosurgery, Neurosurgery Department, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Mohammadreza Emamhadi محمدرضا امام هادی 10031947532846002985 10031947532846002985 No MD, Associate Professor of Neurosurgery, Neurosurgery Department, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Hamid Behzadnia حمید بهزادنیا 10031947532846002986 10031947532846002986 No MD, Assistant Professor of Neurosurgery, Neurosurgery Department, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Maziar Azar مازیار آذر 10031947532846002987 10031947532846002987 No MD, Associate Professor of Neurosurgery, Neurosurgery Department, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Ehsan Kazemnejad-Leili احسان کاظم نزاد لیلی 10031947532846002988 10031947532846002988 No Ph.D, Associate Professor of Biostatistics, Guilan University of Medical Sciences, Rasht, Guilan, Iran Shahrokh Yousefzadeh-Chabok شاهرخ یوسف زاده چابک 10031947532846002989 10031947532846002989 No M.D, Professor of Neurosurgery, Guilan Road Trauma Research Center, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Alireza Razzaghi علیرضا رزاقی 10031947532846002990 10031947532846002990 No MSc in Epidemiology, Guilan Road Trauma Research Center, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran Ali Aramnia علی آرام نیا 10031947532846002991 10031947532846002991 Yes MD, Chief Resident of Neurosurgery, Neurosurgery Department, Poursina Hospital, Guilan University of Medical Sciences, Rasht, Guilan, Iran