Guoquan Zheng

A new method for calculating the exact angle required for spinal osteotomy.

Study Design. Prospective study. Objective. To assess a new method for determining the exact angle required for spinal osteotomy in patients with ankylosing spondylitis (AS). Summary of Background Data. The ideal method for maintaining sagittal balance is to shift the center of gravity of the trunk over the hip axis when pelvic and lower extremity joints are in the neutral position. For patients with AS, various methods have been explored to calculate the required corrective angle. However, these methods carry some limitations. Methods. Twenty patients with AS who underwent spinal osteotomy for correcting kyphotic deformity were studied. Pre- and postoperative full-length freestanding radiographs of the whole spine and pelvis were obtained for all patients. We calculated the ideal postoperative pelvic tilt according to pelvic incidence, and chose the plumbline of the hilus pulmonis rather than C7 as gravity axis of the trunk. Then, the necessary angular correction at the level of osteotomy was calculated. Pre- and postoperative radiological parameters, including Cobb T1–S1, pelvic incidence, pelvic tilt, sacral slope, and sagittal vertical axis were measured. Health related quality of life, including Oswestry Disability Index and Scoliosis Research Society outcomes instrument-22, were administered before surgery and at 6-month follow-up. Results. The preoperative and postoperative Cobb T1–S1 were 52° and 3°, respectively (P < 0.001). All patients demonstrated changes in preoperative to postoperative radiographical parameters including decreased pelvic tilt (from 30° to 11°, P < 0.001) and sagittal vertical axis (from 18 cm to 7 cm), increased sacral slope (from 16° to 35°, P < 0.001), but no significant change in pelvic incidence. Health related quality of life scores at 6-month follow-up had significantly improved compared with those before surgery. Conclusion. This method provides an accurate and reproducible calculation for AS correction. Level of Evidence: 2

Scoliosis model created by pedicle screw tethering in immature goats: the feasibility, reliability, and complications.

Study Design. An in vivo model of scoliosis was established in immature goats. Objective. To assess the feasibility, reliability, and complications of the innovative animal model. Summary of Background Data. Among the methods of creating a scoliotic model, posterior asymmetric tethering of spine yielded encouraging results. However, some shortcomings associated with the use of posterior asymmetric tether are apparent. Methods. Fourteen female goats (age: 5–8 weeks old, weight: 6–8 kg), were instrumented and tethered using unilateral pedicle screws and contralateral rib resections. Twelve of the goats were followed up for 8 weeks by serial radiography. Six goats were removed of the posterior load and no treatment was given. Two goats were selected randomly from the 6 animals and subjected to computed tomography (CT) three-dimensional reconstruction after another 8 weeks. All the 6 goats were killed and spine specimens were harvested for histologic study 16 weeks after observation. Result. Radiographic observation showed that 12 goats developed scoliosis with convex toward the right side, and the curvature increased with time in 11 goats, and it remained unchanged in 1 animal. The angle immediately after the procedures averaged 29.0° (23°–38°) and increased to an average of 43.0° (36.0°–58.0°) over a period of 8 to 10 weeks, with average angle increment being 14.0° (P < 0.001). The curvature ceased to increase in 6 goats during the subsequent 2 months after the tether were removed (P > 0.05). Three-dimensional CT reconstruction revealed that the vertebral bodies were wedged, the 2 sides of the thoracic skeleton were asymmetric, and the vertebrae in the major curve were rotated. Histologic study revealed that the goats remained in growth stage and the growth potential of 2 sides of the spine was not identical. Conclusion. Radiography and three-dimensional CT reconstruction of vertebrae revealed that the architectural alterations found in the model were similar to those of idiopathic-type deformity observed in clinical practice.

Two-level spinal osteotomy for severe thoracolumbar kyphosis in ankylosing spondylitis. Experience with 48 patients.

Study Design. A retrospective study. Objective. To report surgical results for severe thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) corrected with 2-level spinal osteotomy. Summary of Background Data. Transpedicular osteotomy in the lumbar spine is the major approach to correct kyphosis in AS. Most surgical procedures were performed at 1 level and only few literature report 2-level osteotomy in 1 patient. Methods. From January 2003 to June 2011, we reviewed 48 patients experiencing AS with severe thoracolumbar kyphosis who underwent stage 2-level spinal osteotomy in our hospital. The osteotomies were performed at T12 and L2 or L1 and L3, according to the apex of kyphosis. Preoperative and postoperative height, chin-brow vertical angle, sagittal balance, and the sagittal Cobb angle of the vertebral osteotomy segment were documented. Intraoperative, postoperative, and general complications were recorded. Results. The chin-brow vertical angle improved from 65.0° ± 28.0° to 5.0°± 10.0° (P = 0.000) and the sagittal imbalance distance improved from 26.9 ± 10.4 cm to 10.6 ± 5.6 cm (P = 0.000). The mean amount of correction was 24.9° at the superior site of the osteotomy and 38.1° at the inferior site of the osteotomy. Postoperatively, all patients could walk with horizontal vision and lie on their backs. No major acute complications such as death or complete paralysis occurred. Five patients experienced complications such as infections (n = 1) and cerebrospinal fluid leaks (n = 4). Both Oswestry Disability Index and Scoliosis Research Society scores improved largely. Fusion at the osteotomy site was achieved in each patient, and no implant failures were noted. Conclusion. Single-stage 2-level osteotomy can effectively and safely correct kyphotic deformities of the thoracolumbar spine caused by AS. Level of Evidence: 3

Unilateral versus bilateral percutaneous kyphoplasty for osteoporotic vertebral compression fractures: A systematic review and meta-analysis of RCTs.

The purpose of this research was to compare the efficacy and safety of unilateral versus bilateral PKP for osteoporotic vertebral compression fractures (OVCFs). Six databases (Cochrane, PubMed, MEDLINE, EMBASE, SinoMed, and CNKI) were searched without language restrictions. Twelve randomized controlled trials involving a total of 1,030 patients were identified. The results indicate that unilateral PKP had a better degree of pain relief (visual analog scale) than bilateral PKP (p = 0.04; 95%CI = −0.36 to −0.00) with short‐term follow‐up (within 4 weeks) after operation. The radiological outcome assessment with short‐term follow‐up after operation indicates bilateral PKP had a better degree of anterior vertebral height restoration (p = 0.03; 95%CI = −2.58 to −0.14). Operation time and cement dosage were less for unilateral PKP (p < 0.05). There were no differences in complications such as cement leakage and adjacent vertebral fractures between two approaches (p = 0.06 and p = 0.97, respectively). Life quality assessment (SF‐36) indicates unilateral PKP had a better result of bodily pain relief (p < 0.05; 95%CI = 3.93 to 7.48) and general health benefit (p < 0.05; 95%CI = 0.02 to 2.93) with short‐term follow‐up after operation. We suggest that a unilateral PKP is advantageous.

Pulmonary function improvement in patients with ankylosing spondylitis kyphosis after pedicle subtraction osteotomy.

Study Design. A prospective clinical study. Objective. To observe postoperative change in pulmonary function in patients with ankylosing spondylitis (AS) kyphosis after pedicle subtraction osteotomy (PSO). Summary of Background Data. The preoperative pulmonary dysfunction in patients with AS has been reported in several literatures, whereas few research about postoperative changes in pulmonary function with AS kyphosis was published. Methods. A total of 32 (27 males and 5 females) patients with AS were eligibly involved. Twenty-nine (25 males and 4 females) patients completed the follow-up and 3 (2 males and 1 females) patients were lost. Pulmonary function tests, breath-holding time (BHT), and full-length spine radiographs in natural standing position were followed postoperatively. Results. The global kyphosis significantly decreased from 63.0°± 20.3° preoperatively to 15.3°± 10.3° postoperatively and 17.1°± 10.9° at the 2-year follow-up. The BHT before surgery was 32.5 ± 10.1 s, whereas the postoperative BHT had increased to 43.1 ± 8.6 s (P < 0.05). Two patients with AS underwent normal pulmonary function test before operation, whereas there were 19 patients at 2-year follow-up. The clinical improvement rate was 85.2% (23/27). The percent-predicted vital capacity had increased from 68.4% ± 9.5% to 79.4% ± 6.1% at 2-year follow-up (P < 0.05). The percent-predicted forced vital capacity before PSO was 75.5% ± 6.4% and it was 81.0% ± 6.9% at 2-year follow-up (P < 0.05). The improved percent-predicted vital capacity and predicted forced vital capacity had a positive correlation with the correction of global kyphosis (r = 0.6328 and 0.8612, respectively). Conclusion. The postoperative pulmonary function including pulmonary volume and ventilatory function in patients with AS with kyphosis had significantly improved at 2-year follow-up. And, the improved pulmonary function had a positive correlation with the kyphosis correction. Level of Evidence: 3

Porous Ti6Al4V scaffold directly fabricated by sintering: preparation and in vivo experiment

The interface between the implant and host bone plays a key role in maintaining primary and long-term stability of the implants. Surface modification of implant can enhance bone ingrowth and increase bone formation to create firm osseointegration between the implant and host bone and reduce the risk of implant losing. This paper mainly focuses on the fabricating of 3-dimensiona interconnected porous titanium by sintering of Ti6Al4V powders, which could be processed to the surface of the implant shaft and was integrated with bone morphogenetic proteins (BMPs). The structure and mechanical property of porous Ti6Al4V was observed and tested. Implant shaft with surface of porous titanium was implanted into the femoral medullary cavity of dog after combining with BMPs. The results showed that the structure and elastic modulus of 3D interconnected porous titanium was similar to cancellous bone; porous titanium combined with BMP was found to have large amount of fibrous tissue with fibroblastic cells; bone formation was significantly greater in 6 weeks postoperatively than in 3 weeks after operation. Porous titanium fabricated by powders sintering and combined with BMPs could induce tissue formation and increase bone formation to create firm osseointegration between the implant and host bone.

Selection of Lowest Instrumented Vertebra for Thoracolumbar Kyphosis in Ankylosing Spondylitis.

Study Design. Retrospective study. Objective. To determine the optimal osteotomized vertebra (OV) and lowest instrumented vertebra (LIV) in ankylosing spondylitis (AS) kyphosis. Summary of Background Data. Although most of AS kyphosis cases are treated by pedicle subtraction osteotomy (PSO), few studies have focused on the selection of the LIV relative to distal OV. Methods. We reviewed all AS kyphosis cases surgically treated at our institution between 2010 and 2013. Patients were divided into groups based on the relative position of LIV and distal OV: group OV+2, the LIV was the second vertebra below OV; group OV+3, the LIV was the third vertebra below OV; group OV+4, the LIV was the fourth vertebra below OV. The preoperative and 2-year postoperative radiographic parameters and clinical data of the former two groups were compared. In addition, if the LIV was S1, patients were included in group S1, and those remaining were included in group non-S1 (the LIV was L5 or above). Results. None of the patients presented fixation failure. Groups OV+2 and OV+3 had similar magnitudes of kyphosis (P > 0.05) and sagittal vertical axis corrections (P > 0.05) at the last follow-up. There was no difference in the incidence of proximal junctional kyphosis (PJK) between groups (P > 0.05). Between groups S1 and non-S1, the incidence of PJK and the magnitudes of kyphosis and sagittal vertical axis corrections were not significantly different (P > 0.05). The lumbosacral visual analogue scale and the incidence of pressure sores in group S1 were higher than in group non-S1 (P < 0.05). Conclusion. When PSO is performed at the level of L2 or L3, the instrumentation can be limited to the two caudal vertebra that follow. Extending the fixation to more vertebra or to the sacrum does not appear to improve the stability of the instrumentation and the fusion rate, and it is not suitable to carry out PSO at L4. Level of Evidence: 4

Changes of the abdomen in patients with ankylosing spondylitis kyphosis.

Study Design. A retrospective clinical study. Objective. To investigate changes of the abdomen in patients with ankylosing spondylitis kyphosis. Summary of Background Data. Since 1945, many authors had reported the good clinical and radiographical outcomes and higher patient satisfaction rates of spinal osteotomy techniques. However, to our knowledge, whether the visceral and diaphragmatic compression that results from the inferior edge of the thoracic cage is relieved by the surgery has not yet been reported. Materials and Methods. From July 2010 to July 2013, 26 patients (24 males, and 2 females) with severe ankylosing spondylitis kyphosis, who underwent pedicle subtraction osteotomy in the Department of Orthopaedics at Chinese Peoples Liberation Army General Hospital were studied. Preoperative and postoperative computed tomographic scan, 3-dimensional reconstruction, and preoperative pulmonary function test were performed. Via those tests, the minimum distance on the median sagittal plane of the abdomen (MD), the acreage of the abdominal median sagittal plane (AMSPA), the diaphragm angle on median sagittal plane can be gained. A paired sample t test was performed to determine the differences between the preoperative and postoperative AMSPA and MD and diaphragm angle on median sagittal plane, respectively. Postoperative MD/preoperative MD and postoperative AMSPA/preoperative AMSPA and global kyphosis were also analyzed by performing independent sample t test for the 2 groups. Results. The diaphragm angle on median sagittal plane has changed significantly in all the patients. There was significant change of both MD and AMSPA in patients whose abdominal wall was folded into abdomen, whereas neither MD nor AMSPA in patients without the factor. Conclusion. To a certain degree, the diaphragmatic compression and the visceral compression could be compensated for by turning to flattening or even developing into kyphosis of the lumbar lordosis before surgery, which could be corrected by a spinal osteotomy. Sagittal rotation of diaphragm in ankylosing spondylitis kyphosis could also be improved by a spinal osteotomy. Level of Evidence: 4

Positioning thoracic pedicle screw entry point using a new landmark: a study based on 3-dimensional computed tomographic scan.

Study Design. A novel method to identify the entry point. Objective. To quantify the position of thoracic pedicle screw entry points on the lamina at various segments of the thoracic vertebrae in normal subjects and patients with adolescent idiopathic scoliosis and propose a new technique to select entry points using a new landmark. Summary of Background Data. Thoracic pedicle screws have been widely used in thoracic surgery, and the placement of pedicle screws has been studied extensively. However, there are only qualitative studies on selecting the entry point, and no study has quantified the position of entry points. Methods. A retrospective study using 3-dimensional computed tomographic reconstruction techniques were used to study the morphology of thoracic vertebrae in 110 adolescents (56 cases of adolescent idiopathic scoliosis and 54 normal subjects). A quantitative area was used to select the entry point. Thoracic pedicle screw entry point was determined using the new landmark as reference and thoracic pedicle screws were placed in 21 patients. Postoperative computed tomographic scanning was performed to assess the safety and effectiveness of this entry point selection technique. Results. We determined that the accuracy of pedicle screw placing after positioning entry point using the quantitative area was significantly superior to that after positioning entry point using the traditional method (P < 0.05). Conclusion. The new technique quantifies the position of each thoracic pedicle screw entry point and it is convenient, easy to operate, and has relatively high accuracy of screw placement. This positioning technique can provide safe and accurate clinical guidance for selecting thoracic pedicle screw entry point. Level of Evidence: 4

The radiologic, clinical results and digestive function improvement in patients with ankylosing spondylitis kyphosis after pedicle subtraction osteotomy

BACKGROUND CONTEXT Although there have been several reports describing the radiologic and clinical outcomes of pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) with spinal kyphotic deformity, little is known about the digestive function improvement in AS kyphosis after PSO. PURPOSE The aim was to assess radiologic and clinical results and digestive function improvement in patients with AS kyphosis after PSO. STUDY DESIGN/SETTING This was a retrospective clinical study. PATIENT SAMPLE From January 2009 to July 2013, 53 patients in our department with AS kyphotic deformity who underwent PSO were reviewed. OUTCOME MEASURES The globe kyphosis (GK) was measured. A health-related quality of life included Oswestry Disability Index (ODI) and Scoliosis Research Society outcomes instrument-22 (SRS-22). The acreage of the abdominal median sagittal plane (AMSPA) and the minimum distance (MD) between the xiphoid process and the spine or between the abdominal wall and the spine when the abdominal wall was folded into abdomen were measured on the three-dimensional computed tomography scans. The positional changes of abdominal viscera, such as the liver, spleen, and kidney, were also measured. Digestive function assessment included weight and the food intake (FI), and the change of the defecate frequency was recorded. METHODS A paired sample t test was performed to determine the differences between the preoperative and postoperative MD, AMSPA, and weight, respectively. A paired sample t test was also performed to determine the differences between preoperative and postoperative Cobb angles and Oswestry Disability Index (ODI), SRS-22 for all the patients, respectively. A paired sample t test was also performed to determine the positional changes of abdominal viscera. Description date was presented as mean±standard deviation. Additionally, an independent sample t test was performed to determine the differences between the patients (Group 1) who had defecate frequency change and the remaining patients (Group 2) for preoperative GK, age, and disease duration, respectively. An independent sample t test was also performed to determine the differences between the patients (Group A) who had obviously increased FI and the remaining patients (Group B) for preoperative GK, age, and disease duration, respectively. RESULTS All the patients had good radiologic and clinical results, postoperatively. The postoperative positions of the abdominal viscera were changed significantly. The weight, the mass of FI, and the defecate frequency were also changed significantly, postoperatively. The preoperative GK, age, and disease duration were not significantly statistical different between the patients who had defecate frequency change and the remaining patients, respectively. There were also not significantly statistical differences between the patients who had obviously increased FI and the remaining patients in preoperative age and disease duration. There was a significantly statistical difference between the patients who had obviously increased FI and the remaining patients for preoperative GK. CONCLUSIONS The single-level or two-level PSO is an effective and safe technique to correct AS kyphosis. And the conditions of extrusion of viscera by trunk flexion decreased volume of the abdominal cavity, and abnormal visceral positions were improved by the osteotomy, followed with digestive function improvement.