To investigate the effects of postoperative fusion implantation on the mesoscopic biomechanical properties of vertebrae and bone tissue osteogenesis in idiopathic scoliosis, a macroscopic finite element model of the postoperative fusion device was developed, and a mesoscopic model of the bone unit was developed using the Saint Venant sub-model approach. To simulate human physiological conditions, the differences in biomechanical properties between macroscopic cortical bone and mesoscopic bone units under the same boundary conditions were studied, and the effects of fusion implantation on bone tissue growth at the mesoscopic scale were analyzed. The results showed that the stresses in the mesoscopic structure of the lumbar spine increased compared to the macroscopic structure, and the mesoscopic stress in this case is 2.606 to 5.958 times of the macroscopic stress; the stresses in the upper bone unit of the fusion device were greater than those in the lower part; the average stresses in the upper vertebral body end surfaces were ranked in the order of right, left, posterior and anterior; the stresses in the lower vertebral body were ranked in the order of left, posterior, right and anterior; and rotation was the condition with the greatest stress value in the bone unit. It is hypothesized that bone tissue osteogenesis is better on the upper face of the fusion than on the lower face, and that bone tissue growth rate on the upper face is in the order of right, left, posterior, and anterior; while on the lower face, it is in the order of left, posterior, right, and anterior; and that patients' constant rotational movements after surgery is conducive to bone growth. The results of the study may provide a theoretical basis for the design of surgical protocols and optimization of fusion devices for idiopathic scoliosis.
Humans ; Scoliosis/surgery* ; Spinal Fusion/methods* ; Lumbar Vertebrae/surgery* ; Osteogenesis ; Biomechanical Phenomena/physiology* ; Finite Element Analysis

OBJECTIVE: To introduce a scout view scanning technique of back-forward bending CT (BFB-CT) in simulated surgical position for evaluating the remaining real angle and flexibility of thoracolumbar kyphosis secondary to old osteoporotic vertebral compression fracture. METHODS: A total of 28 patients with thoracolumbar kyphosis secondary to old osteoporotic vertebral compression fracture who met the selection criteria between June 2018 and December 2021 were included in the study. There were 6 males and 22 females with an average age of 69.5 years (range, 56-92 years). The injured vertebra were located at T ₁₀-L ₂, including 11 cases of single thoracic fracture, 11 cases of single lumbar fracture, and 6 cases of multiple thoracolumbar fractures. The disease duration ranged from 3 weeks to 36 months, with a median of 5 months. All patients received examinations of BFB-CT and standing lateral full-spine X-ray (SLFSX). The thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), local kyphosis of injured vertebra (LKIV), lumbar lordosis (LL), and the sagittal vertical axis (SVA) were measured. Referring to the calculation method of scoliosis flexibility, the kyphosis flexibility of thoracic, thoracolumbar, and injured vertebra were calculated respectively. The sagittal parameters measured by the two methods were compared, and the correlation of the parameters measured by the two methods was analyzed by Pearson correlation. RESULTS: Except LL ( P>0.05), TK, TLK, LKIV, and SVA measured by BFB-CT were significantly lower than those measured by SLFSX ( P<0.05). The flexibilities of thoracic, thoracolumbar, and injured vertebra were 34.1%±18.8%, 36.2%±13.8%, and 39.3%±18.6%, respectively. Correlation analysis showed that the sagittal parameters measured by the two methods were positively correlated ( P<0.001), and the correlation coefficients of TK, TLK, LKIV, and SVA were 0.900, 0.730, 0.700, and 0.680, respectively. CONCLUSION Thoracolumbar kyphosis secondary to old osteoporotic vertebral compression fracture shows an excellent flexibility and BFB-CT in simulated surgical position can obtain the remaining real angle which need to be corrected surgically.
Male ; Female ; Humans ; Aged ; Fractures, Compression/surgery* ; Spinal Fractures/diagnostic imaging* ; Lumbar Vertebrae/surgery* ; Thoracic Vertebrae/surgery* ; Kyphosis/surgery* ; Osteoporotic Fractures/surgery* ; Lordosis ; Tomography, X-Ray Computed ; Retrospective Studies

OBJECTIVE: To investigate the feasibility of predicting proximal junctional kyphosis (PJK) in adults after spinal deformity surgery based on back-forward Bending CT localization images and related predictive indicators. METHODS: A retrospective analysis was performed for 31 adult patients with spinal deformity who underwent posterior osteotomy and long-segment fusion fixation between March 2017 and March 2020. There were 5 males and 26 females with an average age of 62.5 years (range, 30-77 years). The upper instrumented vertebrae (UIV) located at T ₅ in 1 case, T ₆ in 1 case, T ₉ in 13 cases, T ₁₀ in 12 cases, and T ₁₁ in 4 cases. The lowest instrumented vertebrae (LIV) located at L ₁ in 3 cases, L ₂ in 3 cases, L ₃ in 10 cases, L ₄ in 7 cases, L ₅ in 5 cases, and S ₁ in 3 cases. Based on the full-length lateral X-ray film of the spine in the standing position before and after operation and back-forward Bending CT localization images before operation, the sagittal sequence of the spine was obtained, and the relevant indexes were measured, including thoracic kyphosis (TK), lumbar lordosis (LL), local kyphosis Cobb angle (LKCA) [the difference between the different positions before operation (recovery value) was calculated], kyphosis flexibility, hyperextension sagittal vertical axis (hSVA), T ₂-L ₅ hyperextension C ₇-vertebral sagittal offset (hC ₇-VSO), and pre- and post-operative proximal junctional angle (PJA). At last follow-up, the patients were divided into PJK and non-PJK groups based on PJA to determine whether they had PJK. The gender, age, body mass index (BMI), number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, osteotomy grading, and related imaging indicators were compared between the two groups. The hC ₇-VSO of the vertebral body with significant differences between groups was taken, and the receiver operating characteristic curve (ROC) was used to evaluate its accuracy in predicting the occurrence of PJK. RESULTS: All 31 patients were followed up 13-52 months, with an average of 30.0 months. The patient's PJA was 1.4°-29.0° at last follow-up, with an average of 10.4°; PJK occurred in 8 cases (25.8%). There was no significant difference in gender, age, BMI, number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, and osteotomy grading between the two groups ( P>0.05). Imaging measurements showed that the LL recovery value and T ₈-L ₃ vertebral hC ₇-VSO in the PJK group were significantly higher than those in the non-PJK group ( P>0.05). There was no significant difference in hyperextension TK, hyperextension LL, hyperextension LKCA, TK recovery value, LL recovery value, kyphosis flexibility, hSVA, and T ₂-T ₇, L ₄, L ₅ vertebral hC ₇-VSO ( P>0.05). T ₈-L ₃ vertebral hC ₇-VSO was analyzed for ROC curve, and combined with the area under curve and the comprehensive evaluation of sensitivity and specificity, the best predictive index was hC ₇-L ₂, the cut-off value was 2.54 cm, the sensitivity was 100%, and the specificity was 60.9%. CONCLUSION Preoperative back-forward Bending CT localization image can be used to predict the occurrence of PJK after posterior osteotomy and long-segment fusion fixation in adult spinal deformity. If the patient's T ₈-L ₂ vertebral hC ₇-VSO is too large, it indicates a higher risk of postoperative PJK. The best predictive index is hC ₇-L ₂, and the cut-off value is 2.54 cm.
Male ; Female ; Humans ; Adult ; Middle Aged ; Retrospective Studies ; Blood Loss, Surgical ; Thoracic Vertebrae/surgery* ; Kyphosis/surgery* ; Lordosis/surgery* ; Spinal Fusion/methods* ; Tomography, X-Ray Computed ; Postoperative Complications/diagnostic imaging* ; Lumbar Vertebrae/surgery*

OBJECTIVE: To investigate the changes in spinal-pelvic sagittal parameters from preoperative standing to prone position in old traumatic spinal fractures with kyphosis. METHODS: The clinical data of 36 patients admitted between December 2016 and June 2021 for surgical treatment of old traumatic spinal fractures with kyphosis, including 7 males and 29 females, aged from 50 to 79 years (mean, 63.9 years), were retrospectively analyzed. Lesion segments included 2 cases of T ₁₁, 12 cases of T ₁₂, 2 cases of T _{11, 12}, 4 cases of T ₁₂ and L ₁, 12 cases of L ₁, 2 cases of L ₂, 1 case of L _{2, 3}, and 1 case of L ₃. The disease duration ranged from 4 to 120 months, with an average of 19.6 months. Surgical procedures included Smith-Petersen osteotomy in 4 cases, Ponte osteotomy in 6 cases, pedicle subtraction osteotomy in 2 cases, and improved fourth level osteotomy in 18 cases; the remaining 6 cases were not osteotomized. The bone mineral density ranged from -3.0 to 0.5 T, with a mean of -1.62 T. The spinal-pelvic sagittal parameters from preoperative standing to prone positions were measured, including local kyphosis Cobb angle (LKCA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and PI and LL mismatch (PI-LL). The kyphotic flexibility=(preoperative standing LKCA-preoperative prone LKCA)/preoperative standing LKCA×100%. Spinal-pelvic sagittal parameters were compared between standing position and prone position before operation, and Pearson correlation was used to judge the correlation between the parameters of standing position and prone position before operation. RESULTS: When the position changed from standing to prone, LKCA and TK decreased significantly ( P<0.05), while SS, LL, PT, and PI-LL had no significant difference ( P>0.05). Pearson correlation analysis showed that LL was significantly correlated with SS and PI-LL in both standing and prone positions ( P<0.05), and the correlation strength between LL and SS in prone position was higher than that in standing position. In the standing position, LKCA was significantly correlated with SS and PT ( P<0.05). However, when the position changed from standing to prone, the correlation between LKCA and SS and PT disappeared, while PT and PI-LL was positive correlation ( P<0.05). The kyphotic flexibility was 25.13%-78.79%, with an average of 33.85%. CONCLUSION For the patients of old traumatic spinal fractures with kyphosis, the preoperative LKCA and TK decrease significantly from standing position to prone position, and the correlation between spinal and pelvic parameters also changed, which should be taken into account in the formulation of preoperative surgical plan.
Male ; Female ; Humans ; Spinal Fractures/surgery* ; Standing Position ; Retrospective Studies ; Lumbar Vertebrae/surgery* ; Kyphosis/surgery* ; Lordosis/surgery*

OBJECTIVE: To analyze the early effectiveness of unilateral biportal endoscopy (UBE) laminectomy in the treatment of two-level lumbar spinal stenosis (LSS). METHODS: The clinical data of 98 patients with two-level LSS treated with UBE between September 2020 and December 2021 were retrospectively analyzed. There were 53 males and 45 females with an average age of 59.9 years (range, 32-79 years). Among them, there were 56 cases of mixed spinal stenosis, 23 cases of central spinal canal stenosis, and 19 cases of nerve root canal stenosis. The duration of symptoms was 1.5- 10 years, with an average of 5.4 years. The operative segments were L _{2, 3} and L _{3, 4} in 2 cases, L _{3, 4} and L _{4, 5} in 29 cases, L _{4, 5} and L _5, S ₁ in 67 cases. All patients had different degrees of low back pain, among of which 76 cases were with unilateral lower extremity symptoms and 22 cases were with bilateral lower extremity symptoms. There were 29 cases of bilateral decompression in both segments, 63 cases of unilateral decompression in both segments, and 6 cases of unilateral decompression and bilateral decompression of each segment. The operation time, intraoperative blood loss, total incision length, hospitalization stay, ambulation time, and related complications were recorded. Visual analogue scale (VAS) score was used to assess the low back and leg pain before operation and at 3 days, 3 months after operation, and at last follow-up. The Oswestry disability index (ODI) was used to evaluate the functional recovery of lumbar spine before operation and at 3 months and last follow-up after operation. Modified MacNab criteria was used to evaluate clinical outcomes at last follow-up. Imaging examinations were performed before and after operation to measure the preservation rate of articular process, modified Pfirrmann scale, disc height (DH), lumbar lordosis angle (LLA), and cross-sectional area of the canal (CAC), and the CAC improvement rate was calculated. RESULTS: All patients underwent surgery successfully. The operation time was (106.7±25.1) minutes, the intraoperative blood loss was (67.7±14.2) mL, and the total incision length was (3.2±0.4) cm. The hospitalization stay was 8 (7, 9) days, and the ambulation time was 3 (3, 4) days. All the wounds healed by first intention. Dural tear occurred in 1 case during operation, and mild headache occurred in 1 case after operation. All patients were followed up 13-28 months with an average of 19.3 months, and there was no recurrence or reoperation during the follow-up. At last follow-up, the preservation rate of articular process was 84.7%±7.3%. The modified Pfirrmann scale and DH were significantly different from those before operation ( P<0.05), while the LLA was not significantly different from that before operation ( P=0.050). The CAC significantly improved ( P<0.05), and the CAC improvement rate was 108.1%±17.8%. The VAS scores of low back pain and leg pain and ODI at each time point after operation significantly improved when compared with those before operation, and the differences between each time points were significant ( P<0.05). According to the modified MacNab criteria, 63 cases were excellent, 25 cases were good, and 10 cases were fair, with an excellent and good rate of 89.8%. CONCLUSION UBE laminectomy is a safe and effective technique with little trauma and fast recovery for two-level LSS and the early effectiveness is satisfactory.
Male ; Female ; Humans ; Middle Aged ; Laminectomy ; Spinal Stenosis/surgery* ; Constriction, Pathologic/surgery* ; Low Back Pain ; Retrospective Studies ; Blood Loss, Surgical ; Endoscopy ; Lumbar Vertebrae/surgery* ; Spinal Fusion/methods* ; Decompression, Surgical ; Surgical Wound/surgery* ; Treatment Outcome

OBJECTIVE: To review the application and progress of different minimally invasive spinal decompression in the treatment of lumbar spinal stenosis (LSS). METHODS: The domestic and foreign literature on the application of different minimally invasive spinal decompression in the treatment of LSS was extensively reviewed, and the advantages, disadvantages, and complications of different surgical methods were summarized. RESULTS: At present, minimally invasive spinal decompression mainly includes microscopic bilateral decompression, microendoscopic decompression, percutaneous endoscopic lumbar decompression, unilateral biportal endoscopy, and so on. Compared with traditional open surgery, different minimally invasive spinal decompression techniques can reduce the operation time, intraoperative blood loss, and postoperative pain of patients, thereby reducing hospital stay and saving treatment costs. CONCLUSION The indications of different minimally invasive spinal decompression are different, but there are certain advantages and disadvantages. When patients have clear surgical indications, individualized treatment plans should be formulated according to the symptoms and signs of patients, combined with imaging manifestations.
Humans ; Decompression, Surgical/methods* ; Endoscopy/methods* ; Laminectomy/methods* ; Lumbar Vertebrae/surgery* ; Minimally Invasive Surgical Procedures ; Retrospective Studies ; Spinal Stenosis/surgery* ; Treatment Outcome

Humans ; Lumbosacral Region ; Minimally Invasive Surgical Procedures ; Spinal Fusion ; Lumbar Vertebrae/surgery* ; Treatment Outcome ; Retrospective Studies

OBJECTIVE: To analyze the causes of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy, summarize the clinical results, and propose preventive measures. METHODS: Retrospective analysis was made on the data of 8 cases of lumbar spondylopathy and vertebral fracture treated by oblique lateral interbody fusion in three medical centers from October 2014 to December 2018. All were female, aged from 50 to 81 years with an average of 66.4 years. Disease types included 1 case of lumbar degenerative disease, 3 cases of lumbar spinal stenosis, 2 cases of lumbar degenerative spondylolisthesis and 2 cases of lumbar degenerative scoliosis. Preoperative dual energy X-ray bone mineral density test showed that 2 cases had T-value >-1 SD, 2 cases had T-value -1 to -2.5 SD, and 4 cases had T-value <-2.5 SD. Single segment fusion was in 5 cases, two segment fusion in 1 case and three segment fusion in 2 cases. Four cases were treated with OLIF Stand-alone and 4 cases were treated with OLIF combined with posterior pedicle screw fixation. Postoperative imaging examination showed vertebral fracture, and all of them were single vertebral fracture. There were 2 cases of right lower edge fracture of upper vertebral body at fusion segment, 6 cases of lower vertebral body fracture at fusion segment, and 6 cases with endplate injury and fusion cage partially embedded in vertebral body. Three cases of OLIF Stand-alone were treated with pedicle screw fixation via posterior intermuscular approach, while one case of OLIF Stand-alone and four cases of OLIF combined with posterior pedicle screw fixation were not treated specially. RESULTS: The 5 cases of initial operation and 3 cases of reoperation did not show wound skin necrosis or wound infection. The follow-up time was from 12 to 48 months with an average of 22.8 months. Visual analogue scale (VAS) of low back pain was preoperative decreased from 4 to 8 points (averagely 6.3 points) and postoperative 1 to 3 points (averagely 1.7 points) at the final follow-up. Oswestry disability index (ODI) was preoperative 39.7% to 52.4% (averagely 40.2%), and postoperative 7.9% to 11.2% (averagely 9.5%) at the final follow-up. During the follow-up, there was no loosening or fracture of the pedicle screw system, and no lateral displacement of the fusion cage;however, the fusion cage at the vertebral fracture segment had obvious subsidence. The intervertebral space height of vertebral fracture segment was preoperaive 6.7 to 9.2 mm (averagely 8.1 mm), and postoperative 10.5 to 12.8 mm (averagely 11.2 mm). The improvement rate after operation was 37.98% compared to preoperative. The intervertebral space height at final follow-up was 8.4 to 10.9 mm (averagely 9.3 mm), and the loss rate was 16.71% compared with that after operation. At the final follow-up, interbody fusion was achieved in all cases except for one that could not be identified. CONCLUSION The incidence of vertebral fracture during oblique lateral interbody fusion in the treatment of lumbar spondylopathy is lower, and there are many reasons for fracture, including preoperative bone loss or osteoporosis, endplate injury, irregular shape of endplate, excessive selection of fusion cage, and osteophyte hyperplasia at the affected segment. As long as vertebral fracture is found in time and handled properly, the prognosis is well. However, it still needs to strengthen prevention.
Humans ; Female ; Male ; Spinal Fractures/surgery* ; Retrospective Studies ; Treatment Outcome ; Lumbar Vertebrae/surgery* ; Spondylolisthesis/surgery* ; Scoliosis ; Spinal Fusion/methods*

OBJECTIVE: To compare the short-term clinical efficacy and radiologic differences between oblique lateral interbody fusion(OLIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for degenerative lumbar spondylolisthesis. METHODS: A retrospective analysis was performed on 58 patients with lumbar spondylolisthesis treated with OLIF or MIS-TLIF from April 2019 to October 2020. Among them, 28 patients were treated with OLIF (OLIF group), including 15 males and 13 females aged 47 to 84 years old with an average age of (63.00±9.38) years. The other 30 patients were treated with MIS-TLIF(MIS-TLIF group), including 17 males and 13 females aged 43 to 78 years old with an average age of (61.13±11.10) years. General conditions, including operation time, intraoperative blood loss, postoperative drainage, complications, lying in bed, and hospitalization time were recorded in both groups. Radiological characteristics, including intervertebral disc height (DH), intervertebral foramen height (FH), and lumbar lordosis angle (LLA), were compared between two groups. The visual analogue scale (VAS) and Oswestry disability index (ODI) were used to evaluate the clinical effect. RESULTS: The operation time, intraoperative blood loss, postoperative drainage, lying in bed, and hospitalization time in OLIF group were significantly less than those in the MIS-TLIF group (P<0.05). The intervertebral disc height and intervertebral foramen height were significantly improved in both groups after the operation (P<0.05). The lumbar lordosis angle in OLIF group was significantly improved compared to before the operation(P<0.05), but there was no significant difference in the MIS-TLIF group before and after operation(P>0.05). Postoperative intervertebral disc height, intervertebral foramen height, and lumbar lordosis were better in the OLIF group than in the MIS-TLIF group (P<0.05). The VAS and ODI of the OLIF group were lower than those of the MIS-TLIF group within 1 week and 1 month after the operation (P<0.05), and there were no significant differences in VAS and ODI at 3 and 6 months after the operation between the two groups(P>0.05). In the OLIF group, 1 case had paresthesia of the left lower extremity with flexion-hip weakness and 1 case had a collapse of the endplate after the operation;in the MIS-TLIF group, 2 cases had radiation pain of lower extremities after decompression. CONCLUSION Compared with MIS-TLIF, OLIF results in less operative trauma, faster recovery, and better imaging performance after lumbar spine surgery.
Male ; Female ; Humans ; Middle Aged ; Aged ; Aged, 80 and over ; Adult ; Retrospective Studies ; Spondylolisthesis/surgery* ; Lumbar Vertebrae/surgery* ; Lordosis/surgery* ; Minimally Invasive Surgical Procedures/methods* ; Spinal Fusion/methods* ; Treatment Outcome ; Blood Loss, Surgical ; Postoperative Hemorrhage

OBJECTIVE: To compare the efficacy and muscle injury imaging between oblique lateral lumbar interbody fusion (OLIF) and transforaminal lumbar interbody fusion (TLIF) in the treatment of single-segment degenerative lumbar spinal stenosis. METHODS: The clinical data of 60 patients with single-segment degenerative lumbar spinal stenosis who underwent surgical treatment from January 2018 to October 2019 was retrospectively analyzed. The patients were divided into OLIF groups and TLIF group according to different surgical methods. The 30 patients in the OLIF group were treated with OLIF plus posterior intermuscular screw rod internal fixation. There were 13 males and 17 females, aged from 52 to 74 years old with an average of (62.6±8.3) years old. And 30 patients in the TLIF group were treated with TLIF via the left approach. There were 14 males and 16 females, aged from 50 to 81 years old with an average of (61.7±10.4) years old. General data including operative time, intraoperative blood loss, postoperative drainage volume, and complications were recorded for both groups. Radiologic data including disc height (DH), the left psoas major muscle, multifidus muscle, longissimus muscle area, T2-weighted image hyperintensity changes and interbody fusion or nonfusion were observed. Laboratory parameters including creatine kinase (CK) values on postoperative 1st and 5th days were analyzed. Visual analogue scale(VAS) and Oswestry disability index(ODI) were used to assess clinical efficacy. RESULTS: There was no significant difference in the operative time between two groups(P>0.05). The OLIF group had significantly less intraoperative blood loss and postoperative drainage volume compared to the TLIF group(P<0.01). The OLIF group also had DH better recovery compared to the TLIF group (P<0.05). There were no significant differences in left psoas major muscle area and the hyperintensity degree before and after the operation in the OLIF group (P>0.05). Postoperativly, the area of the left multifidus muscle and longissimus muscle, as well as the mean of the left multifidus muscle and longissimus muscle in the OLIF group, were lower than those in the TLIF group (P<0.05) .On the 1st day and the 5th day after operation, CK level in the OLIF group was lower than that in the TLIF group(P<0.05). On the 3rd day after operation, the VAS of low back pain and leg pain in the OLIF group were lower than those in the TLIF group (P<0.05). There were no significant differences in the ODI of postoperative 12 months, low back and leg pain VAS at 3, 6, 12 months between the two groups(P>0.05). In the OLIF group, 1 case of left lower extremity skin temperature increased after the operation, and the sympathetic chain was considered to be injured during the operation, and 2 cases of left thigh anterior numbness occurred, which was considered to be related to psoas major muscle stretch, resulting in a complication rate of 10% (3/30). In the TLIF group, one patient had limited ankle dorsiflexion, which was related to nerve root traction, two patients had cerebrospinal fluid leakage, and the dural sac was torn during the operation, and one patient had incision fat liquefaction, which was related to paraspinal muscle dissection injury, resulting in a complication rate of 13% (4/30). All patients achieved interbody fusion without cage collapse during the 6- month follow-up. CONCLUSION Both OLIF and TLIF are effective in the treatment of single-segment degenerative lumbar spinal stenosis. However, OLIF surgery has obviously advantages, including less intraoperative blood loss, less postoperative pain, and good recovery of intervertebral space height. From the changes in laboratory indexes of CK and the comparison of the left psoas major muscle, multifidus muscle, longissimus muscle area, and high signal intensity of T2 image on imaging, it can be seen that the degree of muscle damage and interference of OLIF surgery is lower than that of TLIF.
Male ; Female ; Humans ; Middle Aged ; Aged ; Aged, 80 and over ; Retrospective Studies ; Spinal Stenosis/surgery* ; Blood Loss, Surgical ; Lumbar Vertebrae/surgery* ; Spinal Fusion/methods* ; Treatment Outcome ; Pain, Postoperative ; Muscles ; Minimally Invasive Surgical Procedures/methods*