Objective To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis. Methods Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/ min. Results With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P lt; 0.05). In CPS group, the energy absorption gradually decreased (P lt; 0.05); in EPS group, significant difference was found between other different BMD levels (P lt; 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P gt; 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P lt; 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P lt; 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P gt; 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P gt; 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P lt; 0.05). Conclusion Compared with CPS, the EPS can significantly improve the fixation strength, especially in patients with osteopenia or osteoporosis.
【Abstract】 Objective To investigate the effectiveness of surgical treatment for discogenic low back pain (DLBP) by minimally invasive transforaminal lumbar interbody fusion (TLIF) combined with unilateral pedicle screw fixation (UPSF). Methods Between March 2006 and July 2009, 57 patients with single-level DLBP were treated by minimally invasive TLIF combined with UPSF, including 27 males and 30 females with an average age of 45.6 years (range, 38-61 years) and a disease duration of 3.8 years (range, 9 months to 11 years). The involved segments included L2，3 in 2 cases, L3，4 in 5 cases, L4，5 in 29 cases, and L5, S1 in 21 cases. The operative time, incision length, intraoperative blood loss, postoperative drainage volume, hospitalization times, fusion rate, and complications were observed. The effectiveness were evaluated through Oswestry disability index (ODI) and visual analogue score (VAS), and the operative outcomes were compared in different groups classified according to various pressures of the contrast medium and sensitivities to discoblock after inducing consistent pain. Results The operation time, incision length, blood loss, postoperative drainage volume, and hospitalization times were (84.6 ± 37.4) minutes, (3.4 ± 0.6) cm, (132.5 ± 23.2) mL, (58.7 ± 21.4) mL, and (6.5 ± 0.8) days, respectively. All patients were followed up 2 years and 2 months to 5 years and 4 months (mean, 3.2 years). At last follow-up, ODI and VAS scores were significantly improved when compared with preoperative scores (P lt; 0.05). The effectiveness according to ODI were excellent in 27 cases, good in 22 cases, fair in 6 cases, and poor in 2 cases, with an excellent and good rate of 86.0%. All patients acquired b interbody fusion. At last follow-up according to ODI and VAS scores, better results were found in patients of low-pressure sensitive group and high-sensitive discoblock group (P lt; 0.05). Conclusion Minimally invasive TLIF combined with UPSF is reliable for DLBP with minimal surgical trauma, less paravertebral tissue injury, and fewer complications, but the indications for operation must be strictly followed. Patients being sensitive to low-pressure or high-sensitive to discoblock can achieve better surgical results.
Objective To investigate the application value of intraoperative CT navigation in posterior thoracic pedicle screw placement for scoliosis patients. Methods Between October 2009 and December 2011, 46 patients with scoliosis were treated with thoracic pedicle screw placement under intraoperative CT navigation in 21 cases (group A) or under C-arm fluoroscopy in 25 cases (group B). There was no significant difference in age, gender, type of scoliosis, involved segment, and Cobb angle of main thoracic curve between 2 groups (P gt; 0.05). A total of 273 thoracic pedicle screws were placed in group A and 308 screws in group B. The pedicle screw position evaluated and classified by intraoperative CT images according to the Modi et al. method; and the accurate rate, the safe rate, and the potential risk rate of pedicle screws were calculated on the upper thoracic spine (T1-4), the middle thoracic spine (T5-8), the lower thoracic spine (T9-12), and the entire thoracic spine (T1-12). The accuracy and security of thoracic pedicle screw placement were compared between 2 groups. Results On the entire thoracic spine, the accurate rate of group A (93.4%) was significantly higher than that of group B (83.8%), the safe rate of group A (98.9%) was significantly higher than that of group B (92.5%), showing significant differences between 2 groups (P lt; 0.05). However, the potential risk rate of group B (7.5%) was significantly higher than that of group A (1.1%) (P lt; 0.05). On the upper, the middle, and the lower thoracic spines, there was no significant difference in the accurate rate, the safe rate, and the potential risk rate of pedicle screws between 2 groups (P gt; 0.05). According to CT evaluation results, the potential risk pedicle screws were revised or removed during operation. The patients of 2 groups had no neurological deficits through physical examination of nervous system at 3 days after operation. Conclusion Intraoperative CT navigation can improve the accuracy and security of posterior thoracic pedicle screw placement and it can ensure the safety of operation by finding and promptly removing or revising the potential risk pedicle screws.
Objective To explore the surgical feasibil ity and cl inical outcome of transpedicle screw fixation in treatment of atlantoaxial instabil ity and dislocation. Methods From January 2007 to June 2009, 16 patients with atlantoaxial instabil ity and dislocation were treated with transpedicle screw fixation. There were 13 males and 3 females, with a mean age of 42 years (range, 24-61 years). The transpedicle screw fixation was employed in 5 patients with old odontoid fracture (4 of Anderson type II and 1 of type III), in 4 patients with fresh odontoid fracture, in 4 patients with traumatic disruption of transverse atlantal l igament, and in 3 patients with congenital odontoid disconnection for atlantoaxial instabil ity. All patients had symptoms of cervical pain and l imition of cervical motion, 10 patients compl icated by dyscinesia and hypoesthesia of extremities. The Japanese Orthopaedic Association (JOA) score before operation was from 5 to 13, with an average of 8.5. The image examination showed atlantoaxial instabil ity or dislocation in all patients. Granulated autogenous il ium (20-30 g) was placed onto the surface of the posterior arches of both atlas and axis in some patients with old fracture of odontoid process or disruption of transverse atlantal l igament. Results The mean operative time and bleeding amount were 1.6 hours (1.2-2.5 hours) and 100 mL (50-200 mL), respectively. All the incision healed by first intension. All patients were followed up for 3-18 months, with an average of 11.5 months. The JOA score 3 months after operation was from 12 to 17, with an average of 14.2. All screws were successfully placed in atlas and axis. No postoperative compl ications such as vertebral artery injury, dural rupture, exacerbation of neurological symptoms, wound infection, and broken srews were observed in 16 cases. Postoperative radiograph and CT showed that only one screw penetrated into vertebral canal, but there was no neurological symptoms. Bony fusion was observed after 6 to 18 months of operation, and atlantoaxial rotational function in all patients restored satisfactorily, but axial rotation was partially lost. Conclusion Transpedicle screw fixation in upper cervical spine for treatment of atlantoaxial instabil ity and dislocation is safe and rel iable
Objective To biomechanically compare the maximum pull-out strengths among two pedicle screws and three salvage techniques using poly methylmethacrylate (PMMA) augmentation in osteoporotic sacrum, and to determine which PMMA augmentation technique could serve as the salvage fixation for loosening sacral pedicle screws. Methods Eleven sacra were harvested from fresh adult donated cadavers, aged from 66 to 83 years (average 74.4 years) and included 5 men and 6 women. Radiography was used to exclude sacra that showed tumor or inflammatory or any other anatomic abnormal ities. Following the measurement of bone mineral density, five sacral screw fixations were sequentially establ ished on the same sacrum as follows: unicortical pedicle screw (group A), bicortical pedicle screw (group B), unicortical pedicle screw with the traditional PMMA augmentation (group C), ala screw with the traditional PMMA augmentation (group D), and ala screw with a kyphoplasty-assisted PMMA augmentation technique (group E). According to the sequence above, the axial pull-out test of each screw was conducted on a MTS-858 material testing machine. The maximum pull-out forces were measured and compared. The morphologies of PMMA augmented screws after being pulled-out were also inspected. Results The average bone mineral density of 11 osteoporotic specimens was (0.71 ± 0.08) g/cm2 . By observation of the pull-out screws, groups C, D, E showed perfect bonding with PMMA, and group E bonded more PMMA than groups C and D. The maximum pull-out forces of groups A, B, C, D, and E were (508 ± 128), (685 ± 126), (846 ± 230), (543 ± 121), and (702 ± 144) N, respectively. The maximum pull-out strength was significantly higher in groups B, C, and E than in groups A and D (P lt; 0.05), and in group C than in groups B and E (P lt; 0.05). There was no significant difference in pull-out strength between groups A and D, and between groups B and E (P gt; 0.05). Conclusion For sacral screw fixation of osteoporotic patients with bone mineral density more than 0.7 g/cm2, bicortical pedicle screw could acquire significantly higher fixation strength than the unicortical. Once the loosening of pedicle screw occurs, the traditional PMMA augmentation or ala screw with kyphoplasty-assisted PMMA augmentation may serve as a suitable salvage technique.
To analyze the effectiveness of posterior pedicle screw system combined with interbodyfusion in treating lumbar spondylol isthesis. Methods Between January 2005 and January 2009, 26 patients with lumbar spondylol isthesis underwent posterior pedicle screw system combined with interbody fusion, including 11 males and 15 females with an average age of 56.8 years (range, 36-73 years). The disease duration was 7 months to 11 years. The affected lumbars were L3 in 3 cases, L4 in 12 cases, and L5 in 11 cases. According to the Meyerding evaluating system, 21 cases were classified as degree III, 5 cases as degree III-IV, and 1 case as degree IV. The cl inical results were investigated by measuring radiographic measurements, including Taillard index, Boxall index, sl i pping angle, lumbar lordosis angle,and intervertebral height index preoperatively, immediately, 2 weeks and 3 months postoperatively, respectively. SUK’s criteria was used to judge bone graft fusion. Results Primary heal ing of the incisions was achieved in all cases. Allpatients were followed up 25.8 months on average (range, 10-51 months). There were significant differences in Taillardindex, Boxall index, sl i pping angle, lumbar lordosis angle, and intervertebral height index between preoperatively andimmediately, 2 weeks, 3 months after operation (P lt; 0.05). Bone graft fusion was achieved at 3-8 months after operation(mean, 3.5 months); and the fusion rate was 100%. According to Japanese Orthopedic Association (JOA) scoring, theresults were excellent in 17 cases, good in 7 cases, fair in 1 case, and poor in 1 case; and the excellent and good rate was 92.3%. Compl ications occurred in 2 cases, including nail or rod breakage and nerve injury, and they were cured aftertreatment. Conclusion Posterior pedicle screw system combined with interbody fusion treating lumbar vertebralspondylol isthesis can afford sol id internal fixation and achieve a satisfactory reduction, so it maybe an ideal procedure and a worthy recommended method for treating lumbar spondylol isthesis.
Objective To evaluate the therapeutic effects of expandable pedicle screw (EPS) combined with interbody fusion cage on lumbar spondylolisthesis. Methods From June 2004 to March 2008, 23 patients with lumbar spondylolisthesiswere treated, including 9 males and 14 females aged 24-72 years old (average 48.7 years old). The course of the disease varied from 6 months to 6 years (average 30.4 months). There were 18 cases of degenerative spondylol isthesis and 5 of isthmic spondylolisthesis, including 1 case at L3,4 level, 14 at L4,5 level, and 8 at L5 and S1 levels. There were 17 cases of grade I, 4 of grade II, and 2 of grade III (including 1 case of recurrent L5 spondylolysis) according to Meyerding classification system. Posterior lumbar interbody fusion was performed using 48 PLIVIOS interbody fusion cages, and spondylolisthesis reduction and internal fixation were conducted using 84 pieces of EPS. The indications for use of EPS were initial operation with bone mass reduction or osteoporosis, reoperation of previous pedicle instrumentation, intraoperative screw relocation, sacral anchoring, and construct reinforcement. Cl inical outcomes, radiographic reduction of spondylol isthesis and bone fusion of lumbar interbody were evaluated based on JOA score, Boxall index, and Cook criteria. Results The incision healed by first intension in all cases except for one revision case that suffered from postoperative cerebrospinal fluid leakage and obtained delayed-healing without infection 23 days after operation using conservative treatment. No operative compl ications such as nerve and organ injuries were found.All cases were followed up for 12-39 months (average 17.8 months). X-ray exams of spine AP, lateral, fully extended position and fully flexed position view showed all 84 EPS were fully expanded within vertebral body. The improvement rate of JOA at the final follow-up visit was markedly effective in 14 cases, and effective in 5 cases, and noneffective in 4 cases, with a total effective rate of 82.61%. Anatomic reduction was achieved in 14 cases, improvement was obtained in 6 cases, no improvement was observed in 3 cases, and the reduction rate was 86.69%. Lumber interbody fusion was achieved in 20 cases, fixation was achieved in 2 cases, failure was observed in 1 cases, and the fusion rate was 86.69%. Conclusion EPS in complex with interbody fusion cage provides effective reduction, internal fixation and interbody fusion for the reconstruction of lumbar spondylolisthesis.
Objective To explore some operative problems of correcting paralytic scoliosis(PS) by using vertebral pedicle screwsrods system. Methods From May 2000 to May 2005, 18 patients with PS were corrected by screwsrods system which were made of titanium alloy.There were 10 males and 8 females, aging from 11 to 26 years. The primary disease included poliomyelitis in 13 patients and myelodysplasia (MS) in 5 patients (2 cases for second correction) with scoliosis of an average 85° Cobb angle (55-125°). The pelvic obliquity was found in all patients with an average 24° angle (355°).Of the 18 patients,3 cases were given perioperative halo-pelvic traction, 2 cases were given vertebral wedge osteotomy and correction and fixation, the other patients were purely underwent the treatment of pedicle screwrods system implants. Fusion segment at operation ranged from 6 to 15 sections, applied screws the most was 16,the fewest was 6. Results There were no wound infections and neurologic complications, all wounds healed by the first intention. Allscoliosis obtained obvious correction (P＜0.001), the correction rate averaged 52.95% (44%-81%); the majority of lumbar kyphosis and pelvic obliquity were apparently corrected. The average clinical follow-up (16 cases) was 21 months(6-36 months),there was no implants failure. One patient with MS had a worse Cobb magnitude, the other patients had no curve progression (P＞0.05). Conclusion The use of vertebral pedicle screwsrods fixation to multiple vertebral bodys and short segment fusion for PS, the treatment method is reliable and the outcome is satisfactory. While performing the correcting operative procedures, the spinal, pelvic and lower extremity deformities and functions should be all considered as a whole.
Objective To analyze the therapeutic effect of the posterior pedicle screw system combined with interbody fusion cage on lumbarspondylolisthesis. Methods From February 2003 to March 2006, 37 lumbar spondylolisthesis patients were treated with this operation, including21 males and 16 females and aging 3969 years.The affected lumbars were L3(3cases)，L4(23 cases), and L5(11 cases). According to the Meyerdingevaluating system, 12 cases were lassified as degree Ⅰ, 20 cases as degree Ⅱ,and 5 cases as degree Ⅲ. Taillard index, Boxall index, slipping angle, lumbar lordosis angle and intervertebral height index were measured before operation, and 2 weeks and 3 months after operation. Results All patients were followed up 336 months. There were statistically significant differences in Taillard index, Boxall index, slipping angle, lumbar lordosis angle and intervertebral height index between before operation and 2 weeks after operation (P＜0.05),and no statistically significant differences between 2 weeks and 3 months afteroperation(P＞0.05). According to Dewei Zhou’s creterior for scoring, the results were excellent in 27 cases， good in 8 cases，and fair in 2 cases. Theexcellent and good rate was 94.6%. All of the embedded osseous were fused. Thefusing time was from 3 to 8 months (mean 3-9 months). There were no breakageof screw and rod. The position and configuration of the whole cages were good. Conclusion Applying the posterior pedicle screw system combined with interbody fusion cage may achieve synergism in the treatment of lumbar vertebral spondylolisthesis. Above procedure is served as solid internal fixationand offers a satisfactory reduction, and can improve the fusion rate of the spine. So it is an ideal procedure and worthily recommended method for treatment oflumbar vertebral spondylolisthesis.
ObjectiveTo evaluate the clinical efficacy of domestic minimally-invasive percutaneous screw system for thoracolumbar fractures without neurological damage. MethodsSixty patients suffering from unstable thoracolumbar fractures without obvious neurologic deficits treated from January 2011 to April 2012 were studied retrospectively. The patients were divided into two groups:group A (domestic minimally-invasive percutaneous screw system) and group B (imported minimally-invasive percutaneous screw system). Perioperative parameter, pre-and post-operative imaging indexes, visual analog scale (VAS) and modified MacNab evaluation standard were studied for comparison. ResultsAll the patients were followed up from 6 to 18 months with an average of (12.2±3.0) months. The Cobb's angle and anterior height of the fracture vertebral body changed significantly in each group (P<0.05). There was no significant difference in incision size, surgical time, postoperative improvement of Cobb's angle, anterior height of the fracture vertebral body and accuracy of pedicle screw placement between the two groups (P>0.05). ConclusionDomestic minimally-invasive percutaneous screw system is reliable with minimal invasion, which is comparable to imported minimally-invasive percutaneous screw system.