Combined anterior interbody fusion and posterior pedicle screw fixation in patients with degenerative lumbar disc disease

Reoperation and Mortality Rates Following Elective 1 to 2 Level Lumbar Fusion: A Large State Database Analysis

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

Reoperation to lumbar spinal fusion creates significant burden on patient quality of life and healthcare costs. We assessed rates, etiologies, and risk factors for reoperation following elective 1 to 2 level lumbar fusion.

METHODS

Patients undergoing elective 1 to 2 level lumbar fusion were identified using the Health Care Utilization Project (HCUP) state inpatient databases from Florida and California. Patients were tracked for 5 years for any subsequent lumbar fusion. Cox proportional hazard analyses for reoperation were assessed using the following covariates: fusion approach type, age, race, Charlson comormidity index, gender, and length of stay. Distribution of etiologies for reoperation was then assessed.

RESULTS

71, 456 patients receiving elective 1 to 2 level lumbar fusion were included. A 5-year reoperation rate of 13.53% and mortality rate of 2.22% was seen. Combined anterior-posterior approaches (HR = 0.904, p < 0.05) and TLIF (HR = 0.867, p < 0.001) were associated with reduced risk of reoperation compared to stand-alone anterior approaches and non-TLIF posterior approaches. Age, gender, and number of comorbidities were not associated with risk of reoperation. From 1 to 5 years, degenerative disease rose from 43.50% to 50.31% of reoperations; mechanical failure decreased from 37.65% to 29.77%.

CONCLUSIONS

TLIF and combined anterior-posterior approaches for 1 to 2 level lumbar fusion are associated with the lowest rate of reoperation. Number of comorbidities and age are not predictive of reoperation. Primary etiologies leading to reoperation were degenerative disease and mechanical failure. Mortality rate is not increased from baseline following 1 to 2 level lumbar fusion.

Fusion rate and influence of surgery-related factors in lumbar interbody arthrodesis for degenerative spine diseases: a meta-analysis and systematic review

The aim of this meta-analysis and systematic review is to summarize and critically analyze the influence of surgery-related factors in lumbar interbody fusion for degenerative spine diseases. A systematic review of the literature was carried out with a primary search being performed on Medline through PubMed. The 2009 PRISMA flowchart and checklist were taken into account. Sixty-seven articles were included in the analysis: 48 studies were level IV of evidence, whereas 19 were level III. All interbody fusion techniques analyzed have proved to reach a good fusion rate. An overall mean fusion rate of 93% (95% CI 92-95%, p < 0.001) was estimated pooling the selected studies. The influence of sagittal parameters and cages features in fusion rate was not clear. Autograft is considered the gold standard material. The use of synthetic bone substitutes and biological factors alone or combined with bone graft have shown conflicting results. Low level of evidence studies and high heterogeneity (χ² = 271.4, df = 72, p < 0.001; I² = 73.5%, τ² = 0.05) in data analysis could result in the risk of bias. Further high-quality studies would better clarify these results in the future.

Clinical Outcome After Anterior Lumbar Interbody Fusion With a New Osteoinductive Bone Substitute Material: A Randomized Clinical Pilot Study

STUDY DESIGN

Pilot, single-center, single-blinded, parallel-group, randomized clinical study.

OBJECTIVE

The aim of this study was to pilot a randomized clinical study to evaluate whether instrumented anterior lumbar interbody fusion (ALIF) with a new nanocrystalline hydroxyapatite embedded in a silica gel matrix (NH-SiO2) leads to superior radiologic and clinical outcomes at 12-month follow-up compared with instrumented ALIF with homologous bone.

SUMMARY OF BACKGROUND DATA

ALIF completed with interbody cages is an established technique for performing arthrodesis of the lumbar spine. There is ongoing discussion about which cage-filling material is most appropriate. This is the first study to assess the efficacy of NH-SiO2 in ALIF surgery.

MATERIALS AND METHODS

This randomized, clinical, pilot trial included 2 groups of 20 patients with monosegmental or multisegmental degenerative disease of the lumbar spine who were suitable to undergo monosegmental or bisegmental ALIF fusion at the level L4/L5 and L5/S1 with a carbon fiber reinforced polymer ALIF cage filled with either NH-SiO2 or homogenous bone. Primary outcome was postoperative disability as measured by the Oswestry Disability Index (ODI). Secondary outcomes were postoperative radiographic outcomes, pain, and quality of life. Patients were followed 12 months postoperatively.

RESULTS

Mean (±SD) 12-month ODI was 24±17 in the NH-SiO2 group and 27±19 in the homologous bone group (P=0.582). Postoperative radiography, functional outcomes, and quality-of-life indices did not differ significantly between groups at any of the regularly scheduled follow-up visits.

CONCLUSIONS

This clinical study showed similar functional, radiologic, and clinical outcomes 12 months postoperatively for instrumented ALIF procedures with the use of NH-SiO2 or homologous bone as cage filling. In the absence of any relevant differences in outcome, we postulate that the pivotal clinical study should be designed as an equivalence trial.

Multilevel Anterior Lumbar Interbody Fusion Combined with Posterior Stabilization in Lumbar Disc Disease-Prospective Analysis of Clinical and Functional Outcomes

Objective  This was a prospective controlled study with lumbar degenerative disc disease patients submitted to instrumented anterior lumbar interbody fusion (ALIF) combined with posterior stabilization.

Methods  A sample with 64 consecutive patients was operated by the same surgeons over 4 years. Half of the ALIFs occurred at 2 levels, 43.8% at 3 levels, and 6.25% at 1 level. Interbody cages with integrated screws, filled with bone matrix and bone morphogenetic protein 2, were used.

Results  Half of the patients had undergone previous lumbar spine surgeries, 75% presented with associated degenerative listhesis, and 62.5% had posterior lumbar compression disease. Approximately 56% of the sample had at least 1 risk factor for nonunion. The Oswestry index changed from 71.81 ± 7.22 at the preoperative assessment to 24.75 ± 7.82 at the final follow-up evaluation, while the visual analogue pain scale changed from 7.88 ± 0.70 to 2.44 ± 0.87 ( p  < 0.001). Clinical and functional improvements increased with the number of operated levels, proving the efficacy of multilevel ALIF, performed in 93.75% of the sample. The global complication rate was of 7.82%, with no major complications. No cases of nonunion were observed.

Conclusion  Instrumented ALIF combined with posterior stabilization is a successful option for uni- and multilevel degenerative disc disease of the L3 to S1 segments, even in the significant presence of risk factors for nonunion and of previous lumbar surgeries, assuring very satisfactory clinical-functional and radiographic outcomes with a low medium-term complication rate.

Surgical results of a one-stage combined anterior lumbosacral fusion and posterior percutaneous pedicle screw fixation

Objectives:

Lumbosacral fusion through either an anterior or a posterior approach to achieve good lordosis and stability is always a challenging surgical operation and is often accompanied by a higher rate of pseudarthrosis than when other lumbar segments are involved. This study evaluated the clinical and radiological results of lumbosacral fusions achieved through a combined anterior and posterior approach.

Materials and Methods:

From June 2008 to 2012, 20 patients who had L5–S1 instability and stenosis were consecutively treated, first by anterior interbody fusion using an allogenous strut bone graft through the pararectus approach and then by posterior pedicle screw fixation. A minimum of 1-year of clinical and radiological follow-up was conducted. Intraoperative blood loss, surgical time, and any surgery-related complications were recorded. Clinical outcomes were assessed using a visual analog scale (VAS) and the patient's Oswestry Disability Index (ODI) score. After 1 year, radiological outcomes were assessed by analyzing pelvic incidence, lumbar lordosis, and segmental lordosis using static plain films, while fusion stability was assessed using dynamic plain films.

Results:

The mean operative time and blood loss were 215 min and 325 cc, respectively. After 1 year, the VAS and ODI scores had significantly improved, and stable fusion with good lordotic curvature was obtained in all cases.

Conclusion:

The surgical results of the combined procedure are satisfactory in terms of the functional and radiological outcomes. Our method offers advantages regarding both anterior fusion and posterior fixation.

Short-term effects of a dynamic neutralization system (Dynesys) for multi-segmental lumbar disc herniation

PURPOSE

To determine the safety and short-term curative effects of internal fixation using a dynamic neutralization system (Dynesys) for multi-segmental lumbar disc herniation (ms-LDH) with the control group treated by posterior lumbar interbody fusion (PLIF).

METHODS

Forty-five patients with ms-LDH were selected as study group treated with Dynesys and 40 patients as control group with PLIF. The surgical efficacy was evaluated by comparing the visual analogue scale (VAS) scores, the Oswestry Disability Index (ODI) scores and the ROMs of the adjacent segment before and after surgery. The postoperative complications related to the implants were identified.

RESULTS

All patients were followed up for an average duration of over 30 months. Dynesys stabilization resulted in significantly higher preservation of motion at the index level (p < 0.001), and significantly less (p < 0.05) hypermobility at the adjacent segments. VAS for back and leg pain and ODI improved significantly (p < 0.05) with both the methods, but there was no significant difference between the groups.

CONCLUSIONS

The non-fusion fixation system Dynesys is safe and effective regarding short-term curative effects for the treatment of ms-LDH.

Current strategies for the restoration of adequate lordosis during lumbar fusion

Not restoring the adequate lumbar lordosis during lumbar fusion surgery may result in mechanical low back pain, sagittal unbalance and adjacent segment degeneration. The objective of this work is to describe the current strategies and concepts for restoration of adequate lordosis during fusion surgery. Theoretical lordosis can be evaluated from the measurement of the pelvic incidence and from the analysis of spatial organization of the lumbar spine with 2/3 of the lordosis given by the L4-S1 segment and 85% by the L3-S1 segment. Technical aspects involve patient positioning on the operating table, release maneuvers, type of instrumentation used (rod, screw-rod connection, interbody cages), surgical sequence and the overall surgical strategy. Spinal osteotomies may be required in case of fixed kyphotic spine. AP combined surgery is particularly efficient in restoring lordosis at L5-S1 level and should be recommended. Finally, not one but several strategies may be used to achieve the need for restoration of adequate lordosis during fusion surgery.

Lumbar-sacral fusion by a combined approach using interbody PEEK cage and posterior pedicle-screw fixation: clinical and radiological results from a prospective study

INTRODUCTION

This prospective series evaluated the clinical and radiological results of a circumferential lumbar fusion achieved by a combined approach in one stage (anterior then posterior) using interbody PEEK cages and posterior pedicle-screw fixation.

HYPOTHESIS

The combined approach in one stage is a safe and efficient technique with few complications to achieve a fusion with a satisfying clinical and radiological outcome.

MATERIALS AND METHODS

Thirty-nine consecutive patients were prospectively included, with a one-year clinical and radiological minimum follow-up, from December 2008 to July 2011. All patients suffering from degenerative disc disease or low-grade isthmic spondylolisthesis requiring L5S1, L4L5 or L4S1 spinal fusions were included. Clinical outcome was assessed using VAS, ODI and Rolland-Morris scores. Radiological outcome was assessed by analyzing PI, PT, lumbar lordosis, segmental lordosis, disc height, C7/CSFD ratio on full spine radiographies and the quality of bone fusion on a CT scan at 1-year follow-up. Blood loss, surgery time and adverse events were also recorded.

RESULTS

Twenty-nine patients (74%) were operated for a lumbar degenerative disc disease and 10 patients (26%) for an isthmic spondylolisthesis. Mean age was 46 (± 10.1) years old. Clinical outcome were satisfactory. VAS, ODI and Rolland-Morris scores substantially improved. Mean follow-up was 22.5 months (± 8.7). Mean surgery time was 227 min (± 41.4) for complete surgical procedure time. Mean blood loss was 308 mL (± 179.2) for total surgery. Fusion was assessed in all cases. Disc height and segmental lordosis significantly improved in postoperative. The segmental lordosis at operated level(s) increased by 8.5° (± 5) regardless of the level, and by 11.6° (± 6) for L5-S1.

CONCLUSION

The combined procedure meets the requested criteria for a lumbar fusion in terms of clinical and functional results, fusion rates, and restoration of segmental lordosis. It cumulates the advantages of the anterior and posterior approach performed alone and should be considered by surgeons before realizing a lumbar fusion.

One-stage combined lumbo-sacral fusion, by anterior then posterior approach: clinical and radiological results

INTRODUCTION

We intended to prospectively evaluate the clinical and radiological results of lumbo-sacral fusion achieved by a combined approach, anterior then posterior.

MATERIAL AND METHODS

62 patients were consecutively treated at L5-S1, L4-L5 or L4-S1 for degenerative disc disease or low-grade isthmic spondylolisthesis by combined surgery.

RESULTS

Mean operative time and blood loss were 209 min and 308 ml, respectively, including the two approaches. VAS, ODI and Roland-Morris scores significantly improved postoperatively at 1 year (p < 0.005) and fusion was obtained in all cases on the CT scan at 1-year follow-up. Segmental lordosis significantly improved postoperatively (p < 0.05) with a mean gain of 10.2° at L5-S1 and 5.5° at L4-L5.

CONCLUSION

The combined procedure meets the requested criteria for a lumbar fusion in terms of clinical results, functional outcomes, fusion rates while restoring segmental lordosis and disc height. It cumulates the advantages of the anterior and posterior approach performed alone, especially for L5-S1.

A radiological comparison of anterior fusion rates in anterior lumbar interbody fusion

Aim To compare anterior fusion in standalone anterior lumbar interbody fusion (ALIF) using cage and screw constructs and anterior cage-alone constructs with posterior pedicle screw supplementation but without posterior fusion. Methods Eighty-five patients underwent single- or two-level ALIF procedure for degenerative disk disease or lytic spondylolisthesis (SPL). Posterior instrumentation was performed without posterior fusion in all cases of lytic SPL and when the anterior cage used did not have anterior screw through cage fixation. Results Seventy (82%) patients had adequate radiological follow-up at a mean of 19 months. Forty patients had anterior surgery alone (24 single level and 16 two levels) and 30 had front-back surgery (15 single level and 15 two levels). Anterior locked pseudarthrosis was only seen in the anterior surgery-alone group when using the STALIF cage (Surgicraft, Worcestershire, UK) (37 patients). This occurred in five of the single-level surgeries (5/22) and nine of the two-level surgeries (9/15). Fusion was achieved in 100% of the front-back group and only 65% (26/40) of the anterior surgery-alone group. Conclusion Posterior pedicle screw supplementation without posterolateral fusion improves the fusion rate of ALIF when using anterior cage and screw constructs. We would recommend supplementary posterior fixation especially in cases where more than one level is being operated.

Anterior interbody arthrodesis with percutaneous posterior pedicle fixation for degenerative conditions of the lumbar spine

This is a retrospective case series to evaluate clinical variables, complications and outcome of 50 patients who underwent anterior lumbar interbody fusion (ALIF) supplemented with posterior percutaneous pedicle screw fixation for degenerative conditions of the lumbar spine. Twenty-four patients underwent single-level fusion and 26 patients had a two-level fusion for a total of 76 levels fused. The mean lengths of the anterior and posterior (including repositioning) portions of the procedure were 131 and 102 min, respectively. The mean estimated blood loss for the entire procedure was 288 ml. The overall adverse event rate was 12%. The mean VAS score for leg pain, VAS score for back pain and mean ODI all improved postoperatively. This study found that ALIF using allograft bone and rhBMP-2 combined with percutaneous pedicle screw fixation had a high fusion rate and a low incidence of perioperative complications. Patient outcomes showed significant improvements in back and leg pain and physical functioning.

Anterior lumbar interbody fusion with stand-alone interbody cage in treatment of lumbar intervertebral foraminal stenosis : comparative study of two different types of cages

OBJECTIVE

This retrospective study was performed to evaluate the clinical and radiological results of anterior lumbar interbody fusion (ALIF) using two different stand-alone cages in the treatment of lumbar intervertebral foraminal stenosis (IFS).

METHODS

A total of 28 patients who underwent ALIF at L5-S1 using stand-alone cage were studied [Stabilis(R) (Stryker, Kalamazoo, MI, USA); 13, SynFix-LR(R) (Synthes Bettlach, Switzerland); 15]. Mean follow-up period was 27.3 +/- 4.9 months. Visual analogue pain scale (VAS) and Oswestry disability index (ODI) were assessed. Radiologically, the change of disc height, intervertebral foraminal (IVF) height and width at the operated segment were measured, and fusion status was defined.

RESULTS

Final mean VAS (back and leg) and ODI scores were significantly decreased from preoperative values (5.6 +/- 2.3 --> 2.3 +/- 2.2, 6.3 +/- 3.2 --> 1.6 +/- 1.6, and 53.7 +/- 18.6 --> 28.3 +/- 13.1, respectively), which were not different between the two devices groups. In Stabilis(R) group, postoperative immediately increased disc and IVF heights (10.09 +/- 4.15 mm --> 14.99 +/- 1.73 mm, 13.00 +/- 2.44 mm --> 16.28 +/- 2.23 mm, respectively) were gradually decreased, and finally returned to preoperative value (11.29 +/- 1.67 mm, 13.59 +/- 2.01 mm, respectively). In SynFix-LR(R) group, immediately increased disc and IVF heights (9.60 +/- 2.82 mm --> 15.61 +/- 0.62 mm, 14.01 +/- 2.53 mm --> 21.27 +/- 1.93 mm, respectively) were maintained until the last follow up (13.72 +/- 1.21 mm, 17.87 +/- 2.02 mm, respectively). The changes of IVF width of each group was minimal pre- and postoperatively. Solid arthrodesis was observed in 11 patients in Stabilis group (11/13, 84.6%) and 13 in SynFix-LR(R) group (13/15, 86.7%).

CONCLUSION

ALIF using stand-alone cage could assure good clinical results in the treatment of symptomatic lumbar IFS in the mid-term follow up. A degree of subsidence at the operated segment was different depending on the device type, which was higher in Stabilis(R) group.

Vascular injury in elective anterior lumbosacral surgery

STUDY DESIGN

Systematic review.

OBJECTIVE

To document the incidence and consequences of vascular injury in lumbosacral surgery, to identify factors contributing to this injury, and to determine whether there are any effective measures to decrease the occurrence of vascular injury.

SUMMARY OF BACKGROUND DATA

Anterior lumbosacral surgery encompasses all aspects of spine surgery, including trauma, deformity, and degenerative conditions. Although it has theoretical advantages, anterior lumbosacral surgery carries with it certain definite risks, one of the most critical of which is injury to the surrounding vasculature. It is important for both the patient and the surgeon to understand the risks, patterns, and outcomes of injury to the vascular structures associated with this surgery.

METHODS

A systematic review of the English-language literature was undertaken for articles published between January 1993 and December 2008. Electronic databases and reference lists of key articles were searched to identify published studies examining vascular injury in anterior lumbosacral surgery. Vascular injury was defined as any case in which a suture was required to control bleeding. Two independent reviewers assessed the strength of literature using the Grading of Recommendations Assessment, Development, and Evaluation criteria assessing quality, quantity, and consistency of results. Disagreements were resolved by consensus.

RESULTS

A total of 88 articles were initially screened, and 40 ultimately met the predetermined inclusion criteria. Vascular injuries after anterior lumbosacral surgeries were rare (<5%). Venous laceration was more common than arterial laceration, and most venous injuries occurred during retraction of the great vessels. In most cases, the overall clinical outcome after vascular injury was not adversely affected. L4-L5 exposure was associated with increased vascular injury in some studies but not others. Vascular injury occurred more frequently in laparoscopic compared with open anterior lumbar interbody fusion.

CONCLUSION

Vascular injury in anterior lumbosacral surgery remains low, with reports being <5%. The consequences of injury seem rare, but may include thrombosis, pulmonary embolism, and prolonged hospitalization. Exposure and surgery at L4-L5 may be associated with a higher risk of injury than that at L5-S1, though the data are not consistent.

Clinical follow up after instrumentation-augmented lumbar spinal surgery in patients with unsatisfactory outcomes

Object.

The authors investigated the causes of unsatisfactory outcomes in patients who had undergone instrumentation-assisted lumbar surgery and followed the clinical and imaging results of the revision surgery.

Methods.

Myelography and postmyelography computed tomography (CT) scanning were successfully conducted in 103 patients. In nearly 80% of these patients, the main symptom was back pain, with or without leg pain. Additional electromyography and nerve conduction velocity studies were also conducted in 22 patients in whom CT myelography could not help to establish the definitive cause of surgical failure. There were 26 cases of spinal stenosis, 13 of adjacent-segment instability, 15 of pseudarthrosis, 11 of screw misplacement, four of epidural fibrosis, five of arachnoiditis, seven of disc disruption, and 22 miscellaneous. When conservative treatment failed to relieve symptoms, surgery was suggested whenever an operable lesion was found. Revision surgery was performed in 48 patients, and these cases form the basis of this retrospective cohort study. All patients underwent clinical and imaging follow up for a minimum of 2 years. Two-year clinical outcomes were assessed using the 36-Item Short Form Health Survey questionnaire and compared with earlier scores using the Student t-test. Fusion status was evaluated by two orthopedic surgeons, who examined flexion–extension x-ray films or CT studies.

The greatest improvement after revision surgery was documented in patients with symptoms related to spinal stenosis or disc disruption. Little improvement was observed in patients with misplaced pedicle screws causing nerve injury and those with epidural fibrosis or arachnoiditis.

Conclusions.

Adequate decompression at the initial operation and prevention of restenosis or accelerated adjacent-segment degeneration yielded the most favorable prognosis in the present cases. Successful posterolateral arthrodesis combined with supplemental interbody fusion improved the surgical outcomes in cases involving disc disruption or degeneration.

Cantilever TLIF with structural allograft and RhBMP2 for correction and maintenance of segmental sagittal lordosis: long-term clinical, radiographic, and functional outcome

STUDY DESIGN/SETTING

Prospective cohort study in a tertiary care spine center.

OBJECTIVE

The effectiveness of the cantilever transforaminal lumbar interbody fusion (C-TLIF) technique in creating and maintaining lordosis, avoiding nerve problems, and obtaining fusion was studied.

SUMMARY OF BACKGROUND DATA

C-TLIF is a microscope-assisted transforaminal lumbar interbody fusion technique, emphasizing no dural retraction with placement of structural allograft and RhBMP2 anteriorly under the cortical apophyseal ring, followed by middle column cancellous autograft placed under compression with posterior pedicle spinal instrumentation.

METHODS

A total of 100 consecutive patients studied with an average of 30 months of follow-up. A total of 48 had prior surgery at the index level; 16 had the procedure done at an adjacent level to a previous fusion; 32 at L5-S1 with 42 at L4-L5 and 26 at L3-L4. There were 76 single-level and 24 two-level fusions. One patient was a smoker with one other patient a compensation case. Outcome was prospectively documented with self-administered Visual Analog Pain Scale, Oswestry Disability Questionnaire, Treatment Intensity Questionnaire, and SF-36 Health Survey. Patients rated the surgery as excellent, good, fair, or poor and whether they would recommend the surgery. Student t test was used for statistical analysis with significance set at P = 0.05.

RESULTS

Blood loss and hospital stay averaged 300 mL and 2.2 days, respectively. There was significant reduction (P < 0.05) in pain scores from 9 to 3, Oswestry Disability Index scores from 35 to 12, and Treatment Intensity Score from 21/25 to 2/25 at final follow-up. The SF-36 PCS and MCS scores showed an increasing trend to improvement. A total of 69 rated the surgery as excellent, 23 good, 7 fair, and 1 poor. A total of 97% were satisfied and would recommend the surgery. All had improvement in radicular pain with no dural tears, neural injury, or neuropathic pain. There was significant improvement (P < 0.05) in segmental sagittal lordosis from 2 degrees to 9 degrees, anterior disc height from 6 to 14 mm, and posterior disc height from 4 to 8 mm. There was no subsidence, misplaced screws, or instrumentation failure. Solid fusion was obtained in 99 of 100 patients.

CONCLUSIONS

The C-TLIF allows for creation and maintenance of sagittal lordosis while avoiding subsidence and neurologic problems with a 99% fusion rate and 97% patient satisfaction.

Augmentation of anterior lumbar interbody fusion with anterior pedicle screw fixation: demonstration of novel constructs and evaluation of biomechanical stability in cadaveric specimens

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) has proven effective for indications including discogenic back pain, nonunion, and instability. Current practice involves posterior pedicle screw augmentation of the ALIF procedure (ALIF-PPS). This approach requires intraoperative repositioning of the patient for percutaneous posterior pedicle screw placement. We have developed a novel technique in which the ALIF procedure is augmented with anterior pedicle screws (APS; ALIF-APS). In this study, we introduce this new technique and compare the biomechanical stability of the novel ALIF-APS with the current standard ALIF-PPS.

METHODS

The technique was demonstrated in a cadaveric L4-S1 specimen using neuronavigation and fluoroscopy. Plain radiographs and computed tomographic scans of the construct were obtained. Twelve cadaveric spines (7 men and 5 women) from donors with an average age of 81 years (range, 64-93 yr) were then harvested from L4-S1. Six specimens were dedicated to ALIF-APS constructs, and the remaining six were dedicated to ALIF-PPS constructs. The specimens were then studied at L5-S1 in the following steps: 1) intact form, 2) after anterior discectomy, 3) after implantation of titanium cages (ALIF), and 4) after APS or PPS fixation in conjunction with the ALIF. Measurements were obtained in axial rotation and left and right lateral bending flexion-extension. Data were normalized by calculating the ratio of the stiffness of the instrumented to the intact spine. Statistical analyses were then performed on the data.

RESULTS

Radiographs and computed tomographic scans of the construct showed accurate placement of the APS at L5 and S1. The normalized data showed that ALIF-APS and ALIF-PPS had approximately equal stability in axial rotation (1.17 +/- 0.43 versus 0.85 +/- 0.14), lateral bending (0.93 +/- 0.22 versus 0.95 +/- 0.16), and flexion- extension (0.77 +/- 0.13 versus 0.84 +/- 0.2). Paired t test analysis did not show a significant difference between the biomechanical stiffness of ALIF-APS and ALIF-PPS in axial rotation, lateral bending, and flexion-extension.

CONCLUSION

We demonstrate a new technique in a cadaveric specimen whereby the ALIF procedure is augmented with APS fixation using neuronavigation and fluoroscopy. Biomechanical evaluation of the constructs suggests that the ALIF-APS has comparable stability with ALIF-PPS. APS augmentation of ALIF has potential advantages over the current standard ALIF-PPS because it can 1) eliminate the patient repositioning step, 2) minimize the total number of incisions and the total operative time, and 3) protect against dislocation of the ALIF interbody graft or cage. Work is in progress to develop a low-profile system for the novel APS constructs described here.

Vascular injury and complication in neurosurgical spine surgery

Vascular injury is an uncommon, but not rare complication of spine surgery. The consequence of vascular injury may be quite devastating, but its incidence can be reduced by understanding the mechanisms of injury. Properly managing vascular injury can reduce mortality and morbidity of patients. A review of the literature was conducted to provide an update on the etiology and management of vascular injury and complication in neurosurgical spine surgery. The vascular injuries were categorized according to each surgical procedure responsible for the injury, i.e., anterior screw fixation of the odontoid fracture, anterior cervical spine surgery, posterior C1-2 arthrodesis, posterior cervical spine surgery, anterolateral approach for thoracolumbar spine fracture, posterior thoracic spine surgery, scoliosis surgery, anterior lumbar interbody fusion (ALIF), lumbar disc arthroplasty, lumbar discectomy, and posterior lumbar spine surgery. The incidence, mechanisms of injury, and reparative measures were discussed for each surgical procedure. Detailed coverage was especially given to vascular injury associated with ALIF, which may have been underestimated. The accumulation of anatomical knowledge and advanced imaging studies has made complex spine surgery safer and more reliable. It is not clear, however, whether the incidence of vascular injury has been reduced significantly in all procedures of spine surgery. Emerging new techniques, such as microendoscopic discectomy and lumbar disc arthroplasty, seem to be promising, but we need to keep in mind their safety issues, including vascular injury and complication.