Monosegmental Pedicle Instrumentation Research Articles

Biomechanical evaluation of monosegmental pedicle instrumentation in a calf spine model and the role of fractured vertebrae in screw stability.

BackgroundMonsegmental pedicle instrumentation (MSPI) has been used to treat thoracolumbar fractures. However, there are few reports about the biomechanical characteristics of MSPI compared with traditional short-segment pedicle instrumentation (SSPI) in management of unstable thoracolumbar fractures, and the influence of vertebral fracture on screw stability is still unclear.MethodsThis study was to compare the immediate stability between MSPI and SSPI in management of unstable L1 fracture, and to evaluate the role of fractured vertebrae in screw stability. Two studies were performed: in the first study, sixteen fresh calf spines (T11-L3) were divided into two groups, in which unstable fractures at L1 were produced and then instrumented with MSPI or SSPI respectively. The range of motion (ROM) and lax zone (LZ) of specimens were evaluated with pure moment of 6 Nm loaded. The second study measured and compared the pullout strength of screws inserted in to 16 intact and fractured vertebrae of calf spines (L1-3) respectively. The correlation of pullout strength with load sharing classification (LSC) of fractured vertebrae was analyzed.ResultsNo significant difference in the ROM and LZ of the destabilized segments after fixation between MSPI and SSPI, except in axial rotation of ROM (P < 0.05). After fatigue cyclic loading, the MSPI showed a significant increase of ROM during lateral bending and axial rotation (P < 0.05); however, there were no significant differences in the LZ during all loading models between groups (P > 0.05). The mean pullout strength of pedicle screws in fractured vertebrae decreased by 13.7 %, compared with that of intact vertebrae (P > 0.05), and had a low correlation with LSC of the fractured vertebrae (r = 0.293, P > 0.05).ConclusionsMSPI can provide effective immediate stability for management of unstable thoracolumbar fractures; however, it has less fatigue resistance during lateral bending and axial rotation compared with SSPI. LSC score of fractured vertebrae is not a major influence on the pullout strength of screws.

Improved Monosegment Pedicle Instrumentation for Treatment of Thoracolumbar Incomplete Burst Fractures.

Aim. Comparing the clinical results of improved monosegment pedicle instrumentation (iMSPI) and short-segment pedicle instrumentation (SSPI) retrospectively. Method. 63 patients with thoracolumbar incomplete burst fracture were managed with iMSPI or SSPI. 30 patients were managed with iMSPI and fusion. 33 patients were managed with SSPI and fusion. Operative time, blood loss, postoperative drainage, and complications were recorded. Percentage of anterior body height compression (ABHC%) and sagittal index (SI) were obtained preoperatively, one week postoperatively, and at the last followup. Results. The blood loss and postoperative drainage were significantly less in the iMSPI group than in SSPI group (P < 0.05). The follow-up duration of the two groups was not significantly different (P > 0.05). At 12 months postoperatively posterolateral fusion was obtained satisfactorily. Neither preoperative ABHC% and SI nor postoperative SI were significantly different (P > 0.05), but there was a significant difference in postoperative ABHC% (P = 0.000). The ABHC% and SI were not significantly different between the two groups at the last followup (P > 0.05). There were no fixation failures or other complications. Summary. IMSPI yielded satisfactory results similar to those of SSPI in patients with type A3.1/3.2 thoracolumbar fractures. IMSPI is recommended for minor trauma, reducing one-segment fusion, and maximization of the remaining motor function.

Minimally invasive percutaneous mono-segment pedicle instrumentation for thoracolumbar burst fractures

Objective To investigate the feasibility,safety and therapeutic effects of minimally invasive percutaneous mono-segment pedicle instrumentation in treating thoracolumbar burst fractures ( AO classification:A 3.1 and A 3.2 ).Methods Twenty-four inpatients with thoracolumbar burst fractures (AO classification:A 3.1 and A 3.2) treated with percutaneous mono-segment pedicle instrumentation from March 2010 to December 2010 were retrospectively studied.The operation time,blood loss,pre-and post-operative visual analogue scale ( VAS),ratio of anterior height between compressed vertebral body and normal vertebral body and vertebral kyphotic Cobb' s angle were evaluated.Results The operation lasted for (90 ± 25) minutes,with intraoperative blood loss of (20 ± 10) ml.The rate of anterior body height rose from pre-operative (56.5 ± 10.1 ) to (92.3 ± 12.2) one week post-operatively and to (90.2 ± 11.l)at the follow-up one year later.The vertebral kyphotic Cobb' s angle was pre-operative ( 16.5 ± 5.2) °,which was reduced to ( 7.3 ± 2.4 )° at oneweek after surgery and ( 7.9 ± 3.5 )° at the follow-up one year later respectively.The VAS scored ( 7.0 ± 1.2) points before surgery,( 1.2 ±0.7) points at one week after surgery and ( 1.1 ± 6..5) points at the follow-up one year later.The ratio of anterior body height at one week after surgery and at the follow-up one year later were both obviously higher than that before surgery (P ＜ 0.05 ),but the ratio one week postoperatively showed no significant difference in comparison with that one year postoperatively (P ＞0.05).The kyphotic Cobb' s angle had significant decrease at one week after surgery and at the follow-up one year later,as compared with that before operation (P ＜0.0 5).Also,the VAS score showed marked improvement at one week after surgery and at the follow-up one year later.Conclusions Minimally invasive percutaneous mono-segmental pedicle instrumentation is effective and safe for thoracolumbar burst fractures (AO classification:A 3.1and A 3.2),but it is not suitable for thoracolumbar burst fracture with severely compressed vertebra. Key words: Spinal fractures; Fracture fixation, internal; Surgical procedures, minimally invasive

Outcomes of two types of short-segment pedicle screw fixation for thoracolumbar fractures

Objective To investigate the feasibility of mono-segment pedicle instrumentation (MSPI)in management of thoracolumbar fracture (AO classification,A1 and A3) by being compared with short-segment(two-segment) pedicle instrumentation(SSPI).Methods Overall 141 patients with tape A1 or A3 thoracolumbar fractures,aged from 20 to 60 years (average,40.5 years),were enrolled in this prospective study.According to a simple randomized method,35 patients with type A1 fracture and 41 patients with type A3fracture were treated with MSPI,while 26 with type A1 fracture and 39 with type A3 fracture were treated with SSPI.Low back outcome score (LBOS) and ASIA2000 were used to evaluate clinical outcome.Eighteenth month postoperatively was assigned as the last follow up period.Wedge index (WI) and sagittal index (SI) of the affected vertebrae on radiography were measured and compared preoperatively,one week postoperatively and at the final follow-up.Results All patients were followed up successfully.The blood loss and duration of operation of MSPI group were significantly less than that of SSPI group,respectively.However,there were no significant differences of clinical outcome between two groups.For type A1 fracture,correction rate and correction loss of WI in MSPI group were better than those in SSPI group.For type A3 fracture,there were no significant differences of correction rate and correction loss of WI and SI between MSPI group and SSPI group; however,the failure rate of MSPI group was significantly higher than that of SSPI group.Conclusion For type A1 and partial type A3 thoracolumbar fractures,MSPI can provide the same or better fixation with less blood loss and operative duration than SSPI.Since MSPI for type A3.2 thoracolumbar fracture has a higher failure rate,the surgical indication should be strictly controlled. Key words: Thoracic vertebrae; Lumbar vertebrae; Spinal fractures; Spinal fusion

A biomechanical study of monosegmental fixation by pedicle instrumentation in the management of thoracolumbar fractures

Objective To test the biomechanical stability of fixation of thoracolumbar burst fractures (A 3.1 by AO classification) with monosegmental pedicle instrumentation (MSPI). Methods Six specimens of T10-L2 thoracolumbar spine segment were harvested from human donors ranging in age from 27 to 46 years (mean,39 years).Incomplete burst fractures (A3.1 by AO classification) were made at the level of T12 in the specimens using a mechanical dropping hammer.The fractures were fixated with MSPI in the specimens sequentially to restore spinal stability.The specimens in conditions of integrity,fracture and MSPI fixation were tested on the mechanical testing system for biomechanical assessment of the segmental stability.Range of motions (ROM) in flexion-extension and lateral bending were recorded by a 2-camera VICON motion measurement system.The rotational stability was tested by a computer torsional testing machine. Results The ROMs of MSPI specimens in flexion,extension,left and right lateral bending were respectively 0.14°± 0.02°,0.07° ± 0.02°,0.73 ° ± 0.22° and 0.74° ± 0.13°,significantly lower than those of fracture specimens (0.84° ± 0.10°,1.94° ± 0.30°,2.33° ± 0.56° and 2.54° ± 0.44° ) and those of intact specimens (0.46° ±0.05°,1.01° ±0.23°,1.34° ± 0.24° and 1.30° ± 0.31°) ( P ＜ 0.05).The torsional force needed in MSPI specimens was 3103.00 ± 213.11 N,which was not significantly different from that in intact specimens (2654.75 ± 122.90 N) ( P ＞ 0.05) but significantly higher than that in fracture specimens ( 1519.60 ± 100.82 N) ( P ＜ 0.05). Conclusion In the treatment of thoraeolumbar burst fractures (A3.1 by AO classification),MSPI can reconstruct the spinal stability. Key words: Spinal fracture; Fracture fixation, internal; Bone nail; Biomechanics

Retrospective analysis of treatment of thoracolumbar burst fracture using mono-segment pedicle instrumentation compared with short-segment pedicle instrumentation

To investigate the safety and therapeutic effects of mono-segmental pedicle instrumentation (MSPI) in treating thoracolumbar burst fracture (AO classification: A3.1 and A3.2). A retrospective analysis was conducted on 60 cases with thoracolumbar burst fracture (AO classification: A3.1 and A3.2) between April 2005 and February 2010. Half of the 60 inpatients were treated with MSPI, and the other half was treated with short-segment pedicle instrumentation (SSPI). The mean operation time, blood loss, visual analog scale (VAS) and vertebral kyphotic angle before and after surgery were compared. In the MSPI group, the mean operation time was 90±25min, and the blood loss at operation was 180±62ml. The vertebral kyphotic angles were 17.3°±9.3° before surgery, 6.5°±6.5° oneweek after surgery, and 9.5°±6.4° for the latest follow-up. The VAS scores were 7.5±1.4 before surgery, 2.5±0.7 oneweek after surgery, and 1.4±0.8 for the latest follow-up. In the SSPI group, the mean operation time was 101±28min, and the blood loss at operation was 203±88ml. The follow-up duration was 12-64months. The vertebral kyphotic angles were 16.5°±9.1° before surgery, 7.1°±6.9° oneweek after surgery, and 7.5°±5.2° for the latest follow-up. The VAS scores were 6.7±1.5 before surgery, 3.0±0.4 oneweek after surgery, and 1.1±0.6 for the latest follow-up. There were no statistically significant differences between these two groups in the operation time, blood loss at operation, VAS score and vertebral kyphotic angle before and after surgery (p>0.05). The post-surgical VAS scores and vertebral kyphotic angles were significantly decreased in both groups, compared to before surgery (p<0.05). It is safe and effective to treat thoracolumbar burst fractures (AO 3.1 and AO 3.2) with MSPI. The mean operation time, blood loss at operation, post-surgical VAS and vertebral kyphotic angle of the MSPI group are similar, compared to the SSPI group. Further research is needed to find out whether therapeutic effects of MSPI are better than those of conservative treatment in these cases.

Transpedicular Fixation in Management of Thoracolumbar Burst Fractures

A prospective clinical trial was conducted. To compare the clinical and radiologic late results of monosegmental transpedicular fixation versus short-segment pedicle instrumentation (SSPI) in management of thoracolumbar burst fractures and evaluate the efficacy of monosegmental transpedicular fixation. SSPI (1 level above and 1 below the fracture level) are accepted by many surgeons as an accepted technique for the treatment of thoracolumbar burst fractures. To preserve more motion segments, some authors have advocated monosegmental pedicle instrumentation (MSPI). The recent developments showed that MSPI yielded good clinical results; however, there were no report about comparison of clinical outcome between monosegmental and biosegmental transpedicular fixation in management of thoracolumbar burst fractures. Eighty-five patients with thoracolumbar burst fractures fulfilling the inclusion criteria were included in the study. The patients were randomized by a simple method into 2 groups. Group 1 were treated with monosegmental transpedicular fixation (n = 47), and group 2 were treated with biosegmental transpedicular fixation (n = 38). Clinical (Low Back Outcome Score and Oswestry Disability Index) and radiologic (load-sharing classification index, sagittal index, and percentage of anterior body height compression) outcomes were analyzed. The 2 groups were similar in age, follow-up period, and severity of the deformity and fracture. The postoperative and follow-up sagittal index, local kyphosis, percentage of anterior body height compression, and average correction loss in local kyphosis in both groups were not significantly different. The failure rate between the 2 surgical approaches was also not significantly different (group 1 = 6.38% and group 2 = 5.26%). Oswestry Disability Index improved in both groups by >25 points in a similar amount (P = 0.23). The average follow-up Low Back Outcome Score was 74.9 and 60.2 for group 1 and group 2, respectively (P = 0.033). In conclusion, radiologic parameters demonstrated that both MSPI and SSPI are the effective and reliable operative techniques for selected thoracolumbar burst fractures. MSPI shortened the operative time and decreased the amount of blood loss significantly and, thus, offered better clinical results. Nevertheless, long-term studies are supposed to be performed to support the outcomes.

Efficacy of monosegmental pedicle instrumentation in treatment of traumatic thoracolumbar burst fractures

Objective To evaluate the clinical efficacy of monosegmental pedicle instrumentation in management of thoracolumbar burst fractures. Methods A total of 67 patients with traumatic thora-columbar burst fractures (type A3.1 and A3.2) were treated with monosegmental pedicle instrumentation in our department from October 2003 to February 2008. Imageologic effect was observed by measuring sagittal index and wedge index via X-ray and clinical outcomes evaluated by using low back outcome score. Results All operations were performed successfully, with average operation duration of 93 mi-nutes and average intraoperative blood loss of 157 ml. Of all, 65 patients were followed up for 4-27 months (average 19.8 months), which showed that all the patients achieved bony fusion, with no implant failure except for one with screw loosening. The sagittal index and wedge index were 13.06°and 42.9% preoperatively and 4.47° and 21.78% postoperatively, with statistical difference (P <0.01). The final follow-up showed no significant correction loss except for two patients (P < 0.05). The low back outcome scores of all patients at follow-up were improved significantly (P < 0.05). Conclusions Monoseg-mental pedicle instrumentation has advantages of minimal invasion, short operative duration, less blood loss and less vertebral motion segment loss and hence is an effective and reliable operative technique for thoracolumbar burst fractures. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation,internal

The biomechanical study and clinical application of monosegmental pedicle instrumentation by endplate method in the fracture vertebrae for thoracolumbar fracture

To evaluate the biomechanical and clinical effect of the treatment of thoracolumbar fracture with monosegmental pedicle instrumentation in the fracture vertebrae by endplate method. Twenty-four porcine thoracolumbal spinal model, divided into four groups randomly, compared the stability of these four groups through pull-out testing. Retrospective study of 49 patients with thoracolumbar fracture who were treated with this technique, to observe the fusion of bone graft, the height of the anterior and posterior range, the angle of kyphosis and the volume of spinal canal, the loss of rectification, low back pain, and the limitation of activity of lumbar. The endplate method group is more stability than the parallel method group, and the pedicle screw in the fracture vertebrae can get enough stability. After operation all 49 cases achieved satisfactory reduction, strong bone fusion, no reduction loss, no refractoriness low back pain, limitation of motion of lumbar et al. Monosegmental pedicle instrumentation by endplate method in the fracture vertebrae for thoracolumbar fracture can get enough extraction stability, and get satisfied clinical effect.

A comparative study on biomechanical results of posterior mono-segment pedide instrumentationand its combination with bone cement fixation for management of thoracolumbar fractures

Objective To compare the biomechanical properties of mono-segTnent pedicle instru-mentation and its combination with bone cement fixation in treatment of thoracolumbar fractures. Meth-ods Eight fresh specimens of calf spines ( T11 -L3 ) were used for development of incomplete burst frac-ture models at the vertebral body of L1. Mono-segment pedicle instrumentation and its combination with vertebroplasty were respectively applied in each specimen subsequently to restore spinal stability. A cyclic loading with pure moment of 4 Nm was applied to specimens, with load frequency of 0.5 Hz for 2 000 cy-cles. Range of motion (ROM) at flexion/extension, left/right lateral bending and left/right axial rotation of the fixated segment at different status of intact, injury, fixation and cyclic loading was determined by spinal three-dimensional instability test system. Results ROM after treatment with two fixation tech-niques and that at different directions after cyclic loading were distinctly smaller than that of intact and fractured models (P <0.05 ). Under mono-segment pedicle instrumentation combined with bone cement fixation, ROM at flexion, extension, lateral bending and axial rotation was 0.40°, 0. 53°, 0.86° and 0.55° respectively and that after cyclic loading was 0.10°, 0.07°, 0.19° and 0.08°respectively, which were all lower than those of monosegmental fixation, especially at flexion and axial rotation, with statisti-cal difference (P <0.05 ). Conclusions Both fixation techniques can provide instant stabihty of the fractured spine and have good fatigue resistance effect. However, mono-segment pedicle instrumentation is inferior to mono-segment pedicle instrumentation plus bone cement fixation in treatment of fractured verte-bral body at flexion and axial rotation. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation,internal; Biomechanics; Bone cement fixation