en Orthopedic Surgery Orthopedic Surgery Original Research Original Research <p> <strong>Abstract</strong><strong> </strong></p><p> <strong>Background:</strong> Spondylolysis and spondylolisthesis can be associated with significant </p><p> low back pain, especially in physically active adolescents. Non-operative management </p><p> is usually successful in improving symptoms, but surgical intervention is </p><p> occasionally required. The aim of this study was to determine the effect of in situ posterolateral </p><p> fusion in the treatment of refractory cases with spondylolysis. </p><p> <strong>Methods:</strong> In this prospective before and after study, we described our experience </p><p> in13 patients managed by in situ fusion after failing multimodality non-operative </p><p> treatment. All surgical procedures were performed by the senior author and by a similar </p><p> technique. The spondylolytic vertebra and the one below were fused, in situ. Finally, </p><p> clinical outcome and recovery rates of clinical symptoms were evaluated by </p><p> Henderson’s functional capacity and Oswestry Disability Index version 2.1, respectively. </p><p> <strong>Results:</strong> The mean duration of non-operative management was 36 (12-72) </p><p> months. There were 8 males and 5 females. Average pre- and postoperative Oswestry </p><p> Disability Indices were 28.4%±13.7% and 4.9±7.8 respectively (P=0.001, significant). </p><p> All patients had follow-up contact on an average of 42.3 months (range 30 - 62 </p><p> months). Based on Henderson’s clinical outcome functional capacity at the final follow- </p><p> up stage clinical outcomes were excellent in 10, good in 2 and poor in 1 patient. </p><p> The case with poor result had a pseudoarthrosis and was re-oprated. Finally he had an </p><p> excellent outcome. </p><p> <strong>Conclusion:</strong> We accept that the number of our cases is not high significantly but it </p><p> can be claimed that in situ fusion is a safe and effective modality to treat symptomatic </p><p> patients with spondylolysis and low-grade spondylolisthesis. A study with much </p><p> more cases is strongly recommended.</p> spondylolysis, intertransverse fusion, posterolateral approach, in situ fusion 175 182 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-13&slc_lang=en&sid=1 Hamid Behtash 20031947532846001673 20031947532846001673 No Iran University of Medical Sciences, Tehran, Iran. Ebrahim Ameri 20031947532846001674 20031947532846001674 No Iran University of Medical Sciences, Tehran, Iran. Mohamadsaleh Ganjavian 20031947532846001675 20031947532846001675 No Iran University of Medical Sciences, Tehran, Iran. Farzad Omidi-Kashani omidif@mums.ac.ir 20031947532846001676 20031947532846001676 Yes Mashhad University of Medical Sciences, Marzieh Nojomi 20031947532846001677 20031947532846001677 No Iran University of Medical Sciences, Tehran, Iran.