ObjectiveTo analyze the relative position between lumbar plexus and access corridor of minimally invasive lateral transpsoas approach based on magnetic resonance imaging distribution of lumbar plexus by three dimensional reconstruction technique, so as to evaluate approach safety. MethodsThree-dimensional fast imaging employing steady-state acquisition sequences of lumbar spine were performed on 71 patients with lumbar degenerative diseases between July 2012 and January 2015. The axial image distance between the anterior edge of lumbar plexus and sagittal central perpendicular line (SCPL) of disc was determined using the distance formula at the mid-disc space from L1, 2 to L4, 5 level. SCPL was drawn perpendicularly to the sagittal plane of intervertebral disc and it passed through its central point, which is initial dilator trajectory for transpsoas approach. With respect to the SCPL of disc, the distance with a positive value indicated neural tissue posterior to it whereas anterior to it represented by a negative value. ResultsVarious branches of lumbar plexus which passed through the psoas major anterior to the SCPL of disc were identified in 42 (59.2%), 58 (81.7%), and 70 (98.6%) patients at L2, 3, L3, 4, and L4, 5 levels, respectively. It is possible to infer the presence of genitofemoral nerve in accordance with relevant anatomic research. A ventral migration of intrapsoas nerves is identified from L1, 2 to L4, 5 level. All differences between levels were statistically significant (P < 0.05). ConclusionWith respect to the SCPL of disc, a pass way of guide wire or a radiographic reference landmark to place working channel, lumbar plexus lie posterior to it from L1, 2 to L3, 4 level and shift anteriorly to it at L4, 5 level, while genitofemoral nerve locate anterior to the SCPL from L2, 3 to L4, 5 level. Neural retraction may take place during sequential dilation of working channel especially at L4, 5 level.
ObjectiveTo evaluate the effectiveness of modified "eggshell" osteotomy for the treatment of thoracolumbar kyphoscoliosis. MethodBetween April 2009 and June 2014, 19 patients with spinal deformity underwent modified "eggshell" osteotomy consisting of preserving posterior bony structures initially and enlarging surgical field for cancellous bone removal. There were 14 males and 5 females with an average age of 37.8 years (range, 18-76 years) and with a median disease duration of 7 years (range, 1-40 years). The disease causes included ankylosing spondylitis in 13 cases, spinal tuberculosis in 3 cases, and chronic vertebral compression fracture in 3 cases. Eleven patients showed single kyphosis and 8 patients had kyphoscoliosis. Preoperative Cobb angle of kyphosis was (64.2±30.1) °, while Cobb angle of scoliosis was (19.9±12.8) °. Apical vertebraes were T10 in 1 case, L1 in 3 cases, L2 in 7 cases, T10, 11 in 2 cases, T12, L1 in 4 cases, T12-L2 in 1 case, and T10-L1 in 1 case. Preoperative visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score were 6.1±1.9 and 15.2±5.6, respectively. According to Frankel criteria for spinal cord function, 16 cases were rated as grade E and 3 cases as grade D before operation. Cobb angle, VAS, and JOA scors were used to assess relief of symptom. ResultsThe operation time was 215-610 minutes (mean, 343 minutes); intraoperative blood loss ranged from 900 to 3000 mL (mean, 1573 mL). All incisions healed primarily. Delayed onset ischemia-reperfusion injury of spinal cord occurred in 1 case at 6 days after operation, and symptoms alleviated after conservative treatments. All 19 cases were followed up 14-76 months (mean, 46 months). No loosening or breakage of internal fixation was observed during follow-up. Cobb angle of kyphosis, Cobb angle of scoliosis, VAS and JOA scores at 1 week after operation and last follow-up were significantly improved when compared with preoperative ones (P<0.05) . VAS and JOA scores at last follow-up were significantly improved when compared with scores at 1 week after operation (P<0.05) , but no significant difference was found in Cobb angle of both kyphosis and scoliosis between at 1 week after operation and at last follow-up (P>0.05) . At 1 week after operation, the correction rate for kyphosis was 34.1%-93.4% (mean, 62.2%), and the correction rate for scoliosis was 42.4%-100% (mean, 68.9%). At 48 months after operation, 3 patients with preoperative impaired spinal cord function achieved full recovery. ConclusionsModified "eggshell" osteotomy owns the advantages of shorter operation time and less intraoperative blood loss, thus it is able to correct thoracolumbar kyphoscoliosis safely and effectively.