BACKGROUND:Adolescent lumbar disc herniation is the main cause of low back pain in adolescents. At present,most of them are treated by conservativetreatment. When long-term non-surgical treatment attempts,surgery may be necessary to prevent further injury when the patient's symptoms are notsufficiently relieved or when the patient has symptoms of single nerve paralysis or compression of the cauda equina,it is very important to choose a suitable interbody fusion device for the surgical treatment of the patients.OBJECTIVE:To explore the effects of minimally invasive interbody fusion with different heights on lumbar biomechanics in patients with adolescent lumbar disc herniation.METHODS:CT scans of a 17-year-old male patient with adolescent lumbar disc herniation (L4-5 segment herniation) were collected. After the three-dimensional reconstruction of MIMICS,the interbody fusion device equal to and 3 mm higher than the intervertebral space was selected for analysis,so two expandablemixed material interbody fusion devices were designed and reconstructed. Fusion device L:11 mm high front,9 mm high posterior,9 mm wide,28 mmlong,and fusion device H:14 mm high front,11 mm high posterior,11 mm wide,28 mm long and the lumbar fusion device was modeled. The fusion deviceand lumbar spine model were optimized,inversely modeled,and then imported into ABAQUS,and finally the 3D model of lumbar fusion was obtained.The physiological activities of the human body were simulated,such as lumbar extension,forward bending,right bending,and left bending,to obtain thecorresponding stress contours. The biomechanical characteristics of the L4-5 vertebra under seven different working conditions were observed.RESULTS AND CONCLUSION:(1) The maximum stress of the two kinds of fuses was in the condition of forward bending and backward extension,the stress value of H fuses was (18.27±3.80) Mpa and (15.02±3.24) Mpa;the stress value of L fuses was (9.16±0.05) Mpa and (9.17±1.83) Mpa. The stress values of the end plate of the H-fusion in the extension station were (19.11±4.03) Mpa and (16.32±3.72) Mpa respectively. The stress values of the L-fusion end plate were (9.13±0.01) Mpa and (4.92±1.01) Mpa respectively. (2) The stress of H-type fusing end plate was higher than that of L-type fusing end plate except for L-5 end plate at neutral position (P<0.05). (3) Choosing an interbody fusion device with a height of more than 3 mm in the same intervertebral space has a more stable biomechanics.

BACKGROUND:Adolescent lumbar disc herniation is the main cause of low back pain in adolescents. At present,most of them are treated by conservativetreatment. When long-term non-surgical treatment attempts,surgery may be necessary to prevent further injury when the patient's symptoms are notsufficiently relieved or when the patient has symptoms of single nerve paralysis or compression of the cauda equina,it is very important to choose a suitable interbody fusion device for the surgical treatment of the patients.OBJECTIVE:To explore the effects of minimally invasive interbody fusion with different heights on lumbar biomechanics in patients with adolescent lumbar disc herniation.METHODS:CT scans of a 17-year-old male patient with adolescent lumbar disc herniation (L4-5 segment herniation) were collected. After the three-dimensional reconstruction of MIMICS,the interbody fusion device equal to and 3 mm higher than the intervertebral space was selected for analysis,so two expandablemixed material interbody fusion devices were designed and reconstructed. Fusion device L:11 mm high front,9 mm high posterior,9 mm wide,28 mmlong,and fusion device H:14 mm high front,11 mm high posterior,11 mm wide,28 mm long and the lumbar fusion device was modeled. The fusion deviceand lumbar spine model were optimized,inversely modeled,and then imported into ABAQUS,and finally the 3D model of lumbar fusion was obtained.The physiological activities of the human body were simulated,such as lumbar extension,forward bending,right bending,and left bending,to obtain thecorresponding stress contours. The biomechanical characteristics of the L4-5 vertebra under seven different working conditions were observed.RESULTS AND CONCLUSION:(1) The maximum stress of the two kinds of fuses was in the condition of forward bending and backward extension,the stress value of H fuses was (18.27±3.80) Mpa and (15.02±3.24) Mpa;the stress value of L fuses was (9.16±0.05) Mpa and (9.17±1.83) Mpa. The stress values of the end plate of the H-fusion in the extension station were (19.11±4.03) Mpa and (16.32±3.72) Mpa respectively. The stress values of the L-fusion end plate were (9.13±0.01) Mpa and (4.92±1.01) Mpa respectively. (2) The stress of H-type fusing end plate was higher than that of L-type fusing end plate except for L-5 end plate at neutral position (P<0.05). (3) Choosing an interbody fusion device with a height of more than 3 mm in the same intervertebral space has a more stable biomechanics.