Anterior exposure of the spine for removal of lumbar interbody devices and implants

Silicon Nitride as a Biomedical Material: An Overview

Silicon nitride possesses a variety of excellent properties that can be specifically designed and manufactured for different medical applications. On the one hand, silicon nitride is known to have good mechanical properties, such as high strength and fracture toughness. On the other hand, the uniqueness of the osteogenic/antibacterial dualism of silicon nitride makes it a favorable bioceramic for implants. The surface of silicon nitride can simultaneously inhibit the proliferation of bacteria while supporting the physiological activities of eukaryotic cells and promoting the healing of bone tissue. There are hardly any biomaterials that possess all these properties concurrently. Although silicon nitride has been intensively studied as a biomedical material for years, there is a paucity of comprehensive data on its properties and medical applications. To provide a comprehensive understanding of this potential cornerstone material of the medical field, this review presents scientific and technical data on silicon nitride, including its mechanical properties, osteogenic behavior, and antibacterial capabilities. In addition, this paper highlights the current and potential medical use of silicon nitride and explains the bottlenecks that need to be addressed, as well as possible solutions.

Revision for cage migration after transforaminal/posterior lumbar interbody fusion: how to perform revision surgery?

Background

Symptomatic pseudarthrosis and cage migration/protrusion are difficult complications of transforaminal or posterior lumbar interbody fusion (TLIF/PLIF). If the patient experiences severe radicular symptoms due to cage protrusion, removal of the migrated cage is necessary. However, this procedure is sometimes very challenging because epidural adhesions and fibrous union can be present between the cage and vertebrae. We describe a novel classification and technique utilizing a navigated osteotome and the oblique lumbar interbody fusion at L5/S1 (OLIF51) technique to address this problem.

Methods

This retrospective study investigated consecutive patients with degenerative lumbar diseases who underwent TLIF/PLIF. Symptomatic cage migration was evaluated by direct examination, radiography, and/or computed tomography (CT) at 1, 3, 6, 12, and 24 months of follow-up. Cage migration/protrusion was defined as symptomatic cage protrusion > 5 mm from the posterior border of the over and underlying vertebral body compared with initial CT. We evaluated patient characteristics including body mass index, smoking history, fusion level, and cage type. A total of 113 patients underwent PLIF/TLIF (PLIF n = 30, TLIF n = 83), with a mean age of 71.1 years (range, 28–87 years). Mean duration of follow-up was 25 months (range, 12–47 months).

Results

Cage migration was identified in 5 of 113 patients (4.4%). All cases of symptomatic cage migration involved the L5/S1 level and the TLIF procedure. Risk factors for cage protrusion were age (younger), sex (male), and level (L5/S1). The mean duration to onset of cage protrusion was 3.2 months (range, 2–6 months). We applied a new classification for cage protrusion: type 1, only low back pain without new radicular symptoms; type 2, low back pain with minor radicular symptoms; or type 3, cauda equina syndrome and/or severe radicular symptoms. According to our classification, one patient was in type 1, three patients were in type 2, and one patient was in type 3. For all cases of cage migration, revision surgery was performed using a navigated high-speed burr and osteotome, and the patient in group 1 underwent additional PLIF without removal of the protruding cage. Three revision surgeries (group 2) involved removal of the protruding cage and PLIF, and one revision surgery (group 3) involved anterior removal of the cage and OLIF51 fusion.

Conclusions

The navigated high-speed burr, navigated osteotome, and OLIF51 technique appear very useful for removing a cage with fibrous union from the disc in patients with pseudarthrosis. This new technique makes revision surgery after cage migration much safer, and more effective. This technique also reduces the need for fluoroscopy.

Evolution of Complex Spine Surgery in Neurosurgery: From Big to Minimally Invasive Surgery for the Treatment of Spinal Deformity

Spinal instrumentation for adult spinal deformity dates back to the surgical correction of secondary complications from infectious processes, such as Pott's disease and poliomyelitis [1]. With the population aging at a longer life expectancy today, advanced degenerative spinal diseases and idiopathic scoliosis supersede as the most common causes of adult spinal deformity. Correction of the thoracolumbar malignment, specifically, has rapidly evolved with the burgeoning success of spinal instrumentation. The objective of this chapter is to review the metamorphosis of operative principles for adult thoracolumbar deformity, from aggressive osteotomies in the posterior bony elements to minimally invasive surgery (MIS) at the intervertebral disc space.

The comparison between anterior and posterior approaches for removal of infected lumbar interbody cages and a proposal regarding the use of endoscope-assisted technique

Background

In cases of postoperative deep wound infection after interbody fusion with cages, it is often difficult to decide whether to preserve or remove the cages, and there is no consensus on the optimal approach for removing cages. The aim of this study was to investigate the surgical management of cage infection after lumbar interbody fusion.

Methods

A retrospective study was conducted between January 2012 and August 2018. Patients were included if they had postoperative deep wound infection and required cage removal. Clinical outcomes, including operative parameters, visual analog scale, neurologic status, and fusion status, were assessed and compared between anterior and posterior approaches for cage removal.

Results

Of 130 patients who developed postoperative infection and required surgical debridement, 25 (27 levels) were diagnosed with cage infection. Twelve underwent an anterior approach, while 13 underwent cage removal with a posterior approach. Significant differences were observed between the anterior and posterior approaches in elapsed time to the diagnosis of cage infection, operative time, and hospital stay. All patients had better or stationary American Spinal Injury Association impairment scale, but one case of recurrence in adjacent disc 3 months after the surgery.

Conclusions

Both anterior and posterior approaches for cage removal, followed by interbody debridement and fusion with bone grafts, were feasible methods and offered promising results. An anterior approach often requires an additional extension of posterior instrumentation due to the high incidence of concurrent pedicle screw loosening. The use of an endoscope-assisted technique is suggested to facilitate safe removal of cages.

Endplate injury as a risk factor for cage retropulsion following transforaminal lumbar interbody fusion: An analysis of 1052 cases

Although transforaminal lumbar interbody fusion (TLIF) is a widely accepted procedure, major complications such as cage retropulsion (CR) can cause poor clinical outcomes. Endplate injury (EI) was recently identified as a risk factor for CR, present in most levels developing CR. However, most EIs occurred in non-CR levels, and the features of EIs in CR levels remain unknown.The aim of this study was to identify risk factors for CR following TLIF; in particular, to investigate the relationship between EIs and CR, and to explore the features of EIs in CR.Between October 2010 and December 2016, 1052 patients with various degenerative lumbar spinal diseases underwent bilateral instrumented TLIF. Their medical records, radiological factors, and surgical factors were reviewed and factors affecting the incidence of CR were analyzed.Twenty-one patients developed CR. Nine had back pain or leg pain, of which six required revision surgery. A pear-shaped disc, posterior cage positioning and EI were significantly correlated with CR (P < .001, P = .001, and P < .001, respectively). Computed tomography (CT) scans revealed the characteristics of EIs in levels with and without CR. The majority of CR levels with EIs exhibited apparent compression damage in the posterior part of cranial endplate on the decompressed side (17/18), accompanied by caudal EIs isolated in the central portion. However, in the control group, the cranial EIs involving the posterior part was only found in four of the total 148 levels (P < .001). Most of the injuries were confined to the central portion of the cranial or caudal endplate or both endplates (35 in 148 levels, 23.6%). Additionally, beyond cage breaching into the cortical endplate on lateral radiographs, a characteristic appearance of coronal cage misalignment was found on AP radiographs in CR levels with EIs.A pear-shaped disc, posterior cage positioning and EI were identified as risk factors for CR. EI involving the posterior epiphyseal rim had influence on the development of CR. Targeted protection of the posterior margin of adjacent endplates, careful evaluation of intraoperative radiographs, and timely remedial measures may help to reduce the risks of CR.

Risk Factors Affecting Cage Retropulsion into the Spinal Canal Following Posterior Lumbar Interbody Fusion: Association with Diffuse Idiopathic Skeletal Hyperostosis

Study Design

This was a retrospective observational study.

Purpose

We identify risk factors, including physical and surgical factors, and comorbidities affecting cage retropulsion following posterior lumbar interbody fusion (PLIF).

Overview of Literature

Diffuse idiopathic skeletal hyperostosis (DISH) is considered a risk factor for reoperation after PLIF. We evaluated the effect of DISH on cage retropulsion into the spinal canal, which may require surgical revision for severe neurological disorders.

Methods

A total of 400 patients (175 men, 225 women) who underwent PLIF were observed for >1 year. Factors investigated included the frequency of cage retropulsion and surgical revision. In addition, physical (age, sex, disease), surgical (fusion and PLIF levels, cage number, grade 2 osteotomy), and comorbid (DISH, existing vertebral fracture) factors were compared between patients with and without cage retropulsion. Factors related to surgical revision during the observation period were also considered.

Results

Cage retropulsion occurred in 15 patients and surgical revision was performed in 11. Revisions included the replacement of pedicle screws (PSs) with larger screws in all patients and supplementary implants in 10. Among the patients with cage retropulsion, the average PLIF level was 2.7, with DISH present in nine patients and existing vertebral fractures in six. Factors affecting cage retropulsion were diagnoses of osteoporotic vertebral fracture, multilevel fusion, single-cage insertion, grade 2 osteotomy, presence of DISH, and existing vertebral fracture. Multivariable analysis indicated that retropulsion of a fusion cage occurred significantly more frequently in patients with DISH and multilevel PLIF.

Conclusions

DISH and multilevel PLIF were significant risk factors affecting cage retropulsion. Revision surgery for cage retropulsion revealed PS loosening, suggesting that implant replacement was necessary to prevent repeat cage retropulsion after revision.

Mimickers in Spine: Migrated Cages Causing Radiculopathy

The procedure of interbody fusion has become an established treatment for many spine disorders. This arthrodesis can be achieved by hardware (fusion cage) through many approaches. Initially, posterior lumbar interbody fusion was popularized but had some serious neurological complications related to insertion as well as the migration of the cage. Gradually, transforaminal lumbar interbody fusion (TLIF) was introduced, which proved safer as it involves minimal cord handling, and also migration, if any, remains asymptomatic. We had two patients who were operated for interbody fusion using TLIF technique with subsequent posterior migration of the banana-shaped fusion cage 4–6 month after the index surgery. Both patients presented with radiculopathy mimicking a prolapsed intervertebral disc. These were evaluated and operated with the removal of the migrated cages and revision with bigger-size cages with adequate bone grafting. At the 1-year follow-up, both had remission of symptoms, and radiographs showed no subsequent migration. TLIF procedure is an established procedure to achieve arthrodesis in varying spine disorders with promising result. However, there are only a few reports describing cage migration after the procedure and these have been asymptomatic. Revision surgery is contemplated in the setting of neurological compression or instability. A bigger fusion cage in a compressive mode with adequate bone grafting is used to achieve arthrodesis. The principles of interbody fusion must be followed, and utmost precautions must be taken to prevent this unfortunate complication.

Risk factors for medical complications after long-level internal fixation in the treatment of adult degenerative scoliosis

PURPOSE

This study evaluates baseline patient characteristics and surgical parameters for risk factors of medical complications in ASD patients received posterior long level internal fixation.

METHODS

Analysis of consecutive patients who underwent posterior long-level instruction fixation for adult degenerative scoliosis (ADS) with a minimum of two year follow-up was performed. Pre-operative risk factors, intraoperative variables, peri-operative radiographic parameters, and surgical-related risk factors were collected to analyze the effect of risk factors on medical complications. Patients were separated into groups with and without medical complication. Then, complication group was further classified as major or minor medical complications. Potential risk factors were identified by univariate testing. Multivariate logistic regression was used to evaluate independent predictors of medical complications.

RESULTS

One hundred and thirty-one ADS patients who underwent posterior long segment pedicle screws fixation were included. Total medical complication incidence was 25.2%, which included infection (12.2%), neurological (11.5%), cardiopulmonary (7.6%), gastrointestinal (6.1%), and renal (1.5%) complications. Overall, 7.6% of patients developed major medical complications, and 17.6% of patients developed minor medical complications. The radiographic parameters of pre-operative and last follow-up had no significant difference between the groups of medical complications and the major or minor medical complications subgroups. However, the incidence of cerebrospinal fluid leak (CFL) in patients who without medical complications was much lower than that with medical complications (18.4 vs. 42.4%, P = 0.005). Independent risk factors for development of medical complications included smoking (OR = 6.45, P = 0.012), heart disease (OR = 10.07, P = 0.012), fusion level (OR = 2.12, P = 0.001), and length of hospital stay (LOS) (OR = 2.11, P = 0.000). Independent risk factors for development of major medical complications were diabetes (OR 6.81, P = 0.047) and heart disease (OR = 5.99, P = 0.049). Except for the last follow-up, Oswestry Disability Index and visual analog scale of the patient experienced medical complications trend higher score; the clinical outcomes have no significant difference between the medical and major complications groups.

CONCLUSION

Heart disease comorbidity is an independent risk factor for both medical and major medical complications. Smoking, fusion level, and LOS are independent risk factors for medical complication. Diabetes is the independent risk factors for major medical complications.

Application of Lateral Approach for the Removal of Migrated Interbody Cage: Taphole and Fixing Technique

When a revision surgery related with removal of failed interbody cage is required, going through the previous passage can lead to a higher risk of neurological deficits or incidental dural injuries. Recently, the lateral approach has become a popular method instead of the conventional anterior or posterior approaches. The lateral approach is also useful method to remove failed interbody cage previously placed and re-do interbody fusion with lower risks compared to revision surgery via previous passage. However, there is still some difficulty in retrieving the interbody cage from the intervertebral space because of no spacious passage, subsidence, and uncontrolled movable cage. In this study, we introduce our experience that we removed failed interbody cage more easily with only the simple additional steps of making a taphole and fixing the cage using a thread-tipped stick.

Risk factors for cage retropulsion after lumbar interbody fusion surgery: Series of cases and literature review

OBJECTIVE

To identify the risk factors for cage retropulsion after lumbar interbody fusion surgery.

METHODS

667 patients underwent lumbar interbody fusion surgery between November 2011 to December 2014 were retrospectively reviewed by the medical recording system in our institute. 8 patients experiencing cage retropulsion were included and 2 underwent the initial surgery in other hospitals. The clinical outcomes were evaluated by visual analog scores (VAS) and Oswestry Disability Index (ODI). Plain radiographs and three-dimensional computed tomography scans were used to analyze the incidence of cage retropulsion. Data were analyzed by SPSS 19.0.

RESULTS

The incidence of cage retropulsion was 0.90%(6 out of 665) in our institution. There were 6 male and 2 female with an average age of 45.63 ± 15.48(range, 21-60). The average follow-up time was 23.88 ± 12.69 months(range, 6-43 months) and average retropulsion onset time was 2.75 months(range,1-6 months). 6 patients experienced cage retropulsion at L5/S1 and 2 at L4/5. 6 used bullet-shaped cages and two had kidney-shaped cages. Average bed rest time after the initial surgery was 5.75 ± 1.67 days. 6 patients had neurological deficits and underwent revision surgery. Average operation time and blood loss for revision surgery were much higher than those of the initial surgery (P < 0.05). All the patients got a good result in VAS and ODI both from initial surgery and revision surgery (P < 0.05).

CONCLUSIONS

There were multiple risk factors for cage retropulsion after lumbar interbody fusion surgery, including patient factors, radiological characteristics, surgical techniques and postoperative reasons. In case of retropulsion, revision surgery was essential for the patients who presented neurological deficits and conservative treatment was recommended for asymptomatic patients.

Transdural retrieval of a retropulsed lumbar interbody cage: Technical case report

The purpose of this case report was to describe a novel method to retrieve a herniated lumbar interbody cage. Transforaminal lumbar interbody fusion (TLIF) is an increasingly popular method of spinal fixation and fusion. Unexpected retropulsion of an interbody is a rare event that can result in intractable pain or motor compromise necessitating surgical retrieval of the interbody. Both anterior and posterior approaches to removing migrated cages may be associated with significant surgical morbidity and mortality. A 60-year-old woman underwent an L4-S1 TLIF coupled with pedicle screw fixation at a previous hospital 5 years prior to admission. She noted sudden-onset bilateral lower extremity weakness and right-sided foot drop. Magnetic resonance imaging and radiographs were notable for purely centrally herniated interbody. A posterior, midline transdural approach was used to retrieve the interbody. Situated in between nerve rootlets to the ventral canal, this virgin corridor allowed us to easily visualize and protect neurological structures while safely retrieving the interbody. The patient experienced an immediate improvement in symptoms and was discharged on postoperative day 3. At 12-month follow-up, she had no evidence of cerebrospinal fluid (CSF) leak and had returned to normal activities of daily living. While the risk of CSF leak may be higher with a transdural approach, we maintain that avoiding unnecessary retraction of the nerve roots may outweigh this risk. To our knowledge, this is the first case report of a transdural approach for the retrieval of a retropulsed lumbar interbody cage.

Case Series of Anterior Intervertebral Graft Extrusions in Transforaminal Lumbar Interbody Fusion Surgeries

BACKGROUND

According to the published reports, revision surgery is sometimes recommended even in patients with asymptomatic anterior lumbar intervertebral graft migrations. The main purpose of this chart review study was to report on the clinical course and outcomes of patients who had anterior intervertebral graft extrusions after transforaminal lumbar interbody fusion (TLIF).

METHODS

From July 2002 to July 2014, 1259 consecutive TLIF surgeries were performed. These were reviewed, and patients who had anterior intervertebral graft extrusions were identified.

RESULTS

The incidence of graft extrusion was 0.6% (7 of 1259 patients). There were 6 female patients and 1 male patient with an average age of 65.7 years (range, 44-80 years). All patients underwent TLIF with bilateral pedicle screw fixation, and 6 received recombinant human bone morphogenetic protein-2. Graft migrations were diagnosed between 5 days and 8 months postoperatively except for 2 cases in which migration occurred intraoperatively. The patients were closely followed for an average of 27.4 months (range, 12-43 months). All patients remained asymptomatic during the follow-up period and had solid fusion despite extrusions with an average time to fusion of 13 months (range, 10-18 months). No other adverse events occurred during the follow-up period.

CONCLUSIONS

The risks of additional and highly invasive revision surgery should be weighed against the potential short-term and long-term complications associated with graft extrusions or migrations. It was demonstrated that fusion may take longer but can be achieved, and close observation may be adequate for asymptomatic patients.

Technical Note - Lateral Approach to the Lumbar Spine for the Removal of Interbody Cages

Revision surgery to address the migration or fracture of a lumbar interbody cage can be technically challenging. Scar tissue and fibrosis, among other anatomic barriers, can make removal of the cage a complicated procedure, potentially increasing postoperative pain as well as the probability of neurologic deficits. Use of the lateral surgical technique for removal of the cage can avoid these potential complications. In this case report, we describe the removal of interbody cages through a lateral approach in three patients without the necessity of additional posterior hardware revision.

Major surgical treatment of osteoporotic vertebral fractures in the elderly: a comparison of anterior spinal fusion, anterior-posterior combined surgery and posterior closing wedge osteotomy

Study Design

A retrospective study.

Purpose

To clarify the differences among the three major surgeries for osteoporotic vertebral fractures based on the clinical and radiological results.

Overview of Literature

Minimally invasive surgery like balloon kyphoplasty has been used to treat osteoporotic vertebral fractures, but major surgery is necessary for severely impaired patients. However, there are controversies on the surgical procedures.

Methods

The clinical and radiographic results of patients who underwent major surgery for osteoporotic vertebral fracture were retrospectively compared, among anterior spinal fusion (group A, 9 patients), single-stage combined anterior-posterior procedure (group AP, 8 patients) and posterior closing wedge osteotomy (group P, 9 patients). Patients who underwent revision surgery were evaluated just before the revision surgery, and the other patients were evaluated at the final follow-up examination, which was defined as the end point of the evaluations for the comparison.

Results

The operation time was significantly longer in group AP than in the other two groups. The postoperative correction of kyphosis was significantly greater in group P than in group A. Although the differences were not significant, better outcomes were obtained in group P in: back pain relief at the end point; ambulatory ability at the end point; and average loss of correction.

Conclusions

The posterior closing wedge osteotomy demonstrated better surgical results than the anterior spinal fusion procedure and the single-stage combined anterior-posterior procedure.

Anterior dislodgement of a fusion cage after transforaminal lumbar interbody fusion for the treatment of isthmic spondylolisthesis

Transforaminal lumbar interbody fusion (TLIF) is commonly used procedure for spinal fusion. However, there are no reports describing anterior cage dislodgement after surgery. This report is a rare case of anterior dislodgement of fusion cage after TLIF for the treatment of isthmic spondylolisthesis with lumbosacral transitional vertebra (LSTV). A 51-year-old man underwent TLIF at L4-5 with posterior instrumentation for the treatment of grade 1 isthmic spondylolisthesis with LSTV. At 7 weeks postoperatively, imaging studies demonstrated that banana-shaped cage migrated anteriorly and anterolisthesis recurred at the index level with pseudoarthrosis. The cage was removed and exchanged by new cage through anterior approach, and screws were replaced with larger size ones and cement augmentation was added. At postoperative 2 days of revision surgery, computed tomography (CT) showed fracture on lateral pedicle and body wall of L5 vertebra. He underwent surgery again for paraspinal decompression at L4-5 and extension of instrumentation to S1 vertebra. His back and leg pains improved significantly after final revision surgery and symptom relief was maintained during follow-up period. At 6 months follow-up, CT images showed solid fusion at L4-5 level. Careful cage selection for TLIF must be done for treatment of spondylolisthesis accompanied with deformed LSTV, especially when reduction will be attempted. Banana-shaped cage should be positioned anteriorly, but anterior dislodgement of cage and reduction failure may occur in case of a highly unstable spine. Revision surgery for the treatment of an anteriorly dislodged cage may be effectively performed using an anterior approach.

Use of lateral access in the treatment of the revision spine patient

With the rate of spinal surgery increasing, we have seen a concomitant increase in the number of revision cases. It is, therefore, important to have a systematic approach to the management of these complicated patients with unique problems. A thorough understanding of the different pathologies affecting revision spine patients is critical to an effective treatment recommendation. Lateral access is a useful management approach since it can avoid the complications of operating through previous approaches. Furthermore, it possesses certain advantages for treatment in specific circumstances outlined in this paper. Long-term studies are needed to demonstrate the safety and efficacy of the lateral approach compared to the anterior and posterior approaches in the treatment of revision spine patients.

Vascular injuries during anterior exposure of the thoracolumbar spine

BACKGROUND

The aim of this study was to evaluate the vascular injuries, repairs, and complications encountered during anterior thoracolumbar spine exposures.

METHODS

The medical records of patients undergoing anterior spine exposures from January 2004 to June 2010 were retrospectively analyzed.

RESULTS

A total of 269 anterior exposures were performed in 260 patients. The average patient age was 50.1 years, and the average body mass index was 29.0. Female patients represented 146 (54.3%) cases. Previous spinal surgery was noted in 145 (53.9%) cases, and 19 (7.1%) had previous anterior exposure. The median estimated blood loss (EBL) was 300 mL, and there were no postoperative mortalities. A vascular injury occurred in 37 cases (13.8%), with redo anterior exposure (n = 19, 52% vs. 11%; P < 0.001), previous spinal surgery (n = 145, 19% vs. 7%; P = 0.01), and diagnosis of a tumor (n = 14, 36% vs. 12.5%; P = 0.03) being associated with increased vascular injury. A vascular injury resulted in greater EBL (median: 800 mL vs. 300 mL; P < 0.001) and longer hospitalization (median: 7 days vs. 5 days; P = 0.04). Most frequently injured was the left common iliac vein (in 21 of the 37 [52.5%] injured cases). A vascular surgeon performed the exposure in 159 (59.1%) cases. There was a decrease in EBL (250 mL vs. 500 mL; P < 0.001), total incision time (290 minutes vs. 404 minutes; P = 0.002), and length of stay (5 days vs. 6.5 days; P < 0.001) as compared with the operations where the vascular surgeon was not involved in the exposure. These cases also had an increased incidence of any vascular injury (28 vs. 9; P = 0.04). There were no differences between groups regarding vascular injury type, repair type, or the incidence of deep venous thrombosis.

CONCLUSION

Collaboration between spine and vascular teams may result in decreased blood loss and consequently improved morbidity and length of hospital stay.

Analysis of intraoperative difficulties and management of operative complications in revision anterior exposure of the lumbar spine: a report of 25 consecutive cases

PURPOSE

After a first anterior approach to the lumbar spine, formation of adhesions of soft tissues to the spine increases the surgical difficulties and potential for iatrogenic injury during the revision exposure. The objective of this study was to identify the intraoperative difficulties and postoperative complications associated with revision anterior lumbar spine procedures in a single institution.

METHODS

This is a retrospective review of 25 consecutive anterior revision lumbar surgeries in 22 patients (7 men and 15 women) operated on between 1998 and 2011. Patients with trauma or malignancies were excluded. The mean age of the patients at the time of revision surgery was 56 years (range 20-80 years). The complications were analyzed depending on the operative level and the time between the index surgery and the revision.

RESULTS

Six major complications (five intraoperatively and one postoperatively) occurred in five patients (20 %): three vein lacerations (12 %) and two ureteral injuries (8 %), despite the presence of a double-J ureteral stent. The three vein damages were repaired or ligated by a vascular surgeon. One of the two ureteral injuries led to a secondary nephrectomy after end-to-end anastomosis failure; the other necessitated secondary laparotomy for small bowel obstruction.

CONCLUSIONS

Anterior revision of the lumbar spine is technically challenging and is associated with a high rate of vascular or urologic complications. Therefore, the potential complications of the procedure must be weighted against its benefits. When iterative anterior lumbar approach is mandatory, exposure should be performed by an access surgeon in specialized centers that have ready access to vascular and urologic surgeons.

Extrusion of expandable stacked interbody device for lumbar fusion: case report of a complication

STUDY DESIGN

A case report.

OBJECTIVE

We report on the device failure of a polyetherether-ketone expandable cage device with posterior migration of one of its components.

SUMMARY OF BACKGROUND DATA

Posterior migration of transforaminal lumbar interbody fusion cage devices has been reported with static devices, and ours is the first report of an expandable TLIF device failure and posterior migration of one of its components.

METHODS

The patient is a 30-year-old man who had previously failed 3 lumbar surgical procedures and presented for L5-S1 lumbar fusion with pedicle screws and transforaminal interbody fusion.

RESULTS

Postoperative imaging demonstrated posterior migration of one of the failed expandable interbody components with eventual revision surgery and placement of static transforaminal lumbar interbody fusion cages.

CONCLUSION

This is the first case report to describe such complication, and caution must be warranted when using these devices.

Risk factors for cage retropulsion after posterior lumbar interbody fusion: analysis of 1070 cases

STUDY DESIGN

Single-center retrospective study.

OBJECTIVE

We examined the risk factors for cage retropulsion after posterior lumbar interbody fusion (PLIF) performed for patients with degenerative lumbar spinal diseases.

SUMMARY OF BACKGROUND DATA

Although PLIF is a widely accepted procedure, problems remain regarding perioperative and postoperative complications. There are few reported studies identifying specific risk factors for cage retropulsion, one of the implant-related complications after PLIF, although several case reports have been published.

METHODS

Between April 2006 and July 2010, 1070 patients with various degenerative lumbar spinal diseases underwent single- or multilevel PLIF combined with posterolateral fusion, using posterior pedicle screw fixation and box-type cages. Their medical records and preoperative radiographs were reviewed and the factors influencing the incidence of cage retropulsion were analyzed.

RESULTS

There were 9 cases of cage retropulsion (7 men and 2 women; mean age, 68.2 yr), and it developed within 2 months after surgery in all cases. Five patients had low back pain or leg pain, 3 of whom required revision surgery. The mean fusion level was 3.9 (range, 2-5); in 6 of the 9 patients, the cage had migrated at L5/S, 2 at L4/5, and 1 at L3/4. All of the cages were inserted at the end disc level of multilevel fusion procedures. The disc heights and ranges of motion were significantly greater in patients with cage retropulsion, and patients with a pear-shaped disc space also showed a higher rate of cage retropulsion.

CONCLUSION

These results indicate that PLIF at L5/S, a wide disc space with instability, multilevel fusion surgery, and a pear-shaped disc space on lateral radiographs are risk factors for cage retropulsion. The identification of these risk factors should allow us to avoid this complication, and the use of expandable cages is an effective option for such cases.

Perioperative surgical complications of transforaminal lumbar interbody fusion: a single-center experience

OBJECT

Since its original description in 1982, transforaminal lumbar interbody fusion (TLIF) has grown in popularity as a means for achieving circumferential fusion. The authors sought to define the perioperative complication rates of the TLIF procedure at a large academic medical center.

METHODS

For all eligible patients from a consecutive series of 531 TLIF procedures, the institution's complication database and the medical record were reviewed to identify complications. Medical, nonprocedure-related complications such as myocardial infarction and pulmonary embolism were excluded due to inconsistency in the recording of these complications in the database. Rates were calculated for each type of complication, and subgroup analysis was performed to investigate the effect of previous lumbar surgery, and of multilevel versus single-level interbody fusion on complication rates. Odds ratios were calculated and evaluated using chi-square analysis.

RESULTS

Five hundred thirty-one patients underwent a TLIF procedure during the study period. Two hundred forty-four patients (46%) had undergone a previous lumbar operation. Interbody fusion was performed at 1 level in 317 patients, at 2 levels in 188 patients, at 3 levels in 24 patients, and at 4 levels in 2 patients. One hundred thirty-five patients (25.4%) had at least one procedure-related complication. The most common complications were durotomy (14.3% of patients) and infection (3.8% of patients). Symptomatic screw misplacement (2.1% of patients) and interbody cage migration (1.8% of patients) were less common complications. The overall complication rate was greater in those patients who had undergone a previous operation (OR 1.75, 95% CI 1.18-2.59; p < 0.01) and in those who had multilevel surgery (OR 1.54, 95 % CI 1.04-2.28; p = 0.03), and the incidence of durotomy was higher in patients who had a previous operation (OR 1.75, 95% CI 1.07-2.87; p = 0.03). These differences were statistically significant. Durotomy also occurred more frequently in patients who had multilevel interbody fusion (OR 1.49, 95% CI 0.92-2.43; p = 0.13). A trend toward higher infection rates in those patients who underwent multilevel interbody fusion was observed (OR 1.5, 95% CI 0.62-3.68; p = 0.49), but this was not statistically significant. Infection rates did not differ between revision and first-time surgeries.

CONCLUSIONS

Transforaminal lumbar interbody fusion has gained widespread popularity as a procedure for achieving arthrodesis in the lumbar spine. Complications occurred more often in patients undergoing revision surgery or multilevel interbody fusion. Durotomy and infection were the most common complications in this series.

[Revision strategies for ventral implant failure in the lumbar spine exemplified by stand-alone cages]

This article gives a review of the possible revision strategies after repeated operative treatment of degenerative spinal diseases using stand-alone cages. Own clinical experiences and reports from the literature were taken into consideration. Dorsal stabilization is the main consideration for all access routes even if it can be discussed, albeit controversially, whether ventral removal of an installed cage is justified, because this contains a significantly higher perioperative risk. The increased risk of neurological complications by dorsal revision and for vascular complications by ventral access, especially at the L4/5 level must be particularly considered. Clinical data and own experience have shown that in the majority of cases an additional dorsal stabilization should be favored for revision surgery. Currently large clinical studies which deal with the revision problematic of stand-alone cages with respect to the access route are still lacking.

Opção minimamente invasiva lateral para artrodese intersomática tóraco-lombar

OBJETIVO: O objetivo deste artigo é mostrar resultados clínicos e radiográficos do acesso lateral transpoas na experiência brasileira em condições degenerativas do disco intervertebral. MÉTODOS: 46 pacientes foram submetidos à fusão intersomática lombar por via lateral. Dentre os casos, 18 eram do sexo masculino e 28 do sexo feminino, com idade média de 57,3 (84-32 anos) e média de IMC de 25,9 ± 3,1. Todos os pacientes completaram um ano de acompanhamento. Foram coletados exames radiológicos, como raio X e tomografia computadorizada, exame neurológico e resultados clínicos usando os questionários ODI e VAS (costas e membros inferiores). RESULTADOS: Os procedimentos foram realizados, sem ocorrência de complicações intra-operatórias importantes, em uma média de 103,9 ± 105,5 minutos e com menos de 50cc de perda sanguínea. Em oito dos 46 procedimentos (17,4%) foi utilizada suplementação por parafusos pediculares percutâneos por apresentarem instabilidade segmentar. Foram tratados 80 níveis (de um a cinco níveis) tóraco-lombares (de T12-L1 a L4-L5). Os resultados clínicos avaliados pelos questionários revelaram melhora significante de dor logo após uma semana da cirurgia e da função física após seis semanas. A lordose lombar foi de 36,5 ± 14,7 no pré-operatório para 43,4 ± 12,4 no seguimento de 12 meses. Todos os pacientes apresentaram formação óssea após 12 meses da cirurgia. Sete casos foram revisados (15,2%), ainda de forma minimamente invasiva devido à estenose persistente (três casos; 6,5%), afundamento do espaçador (três casos; 6,5%) ou mal-alinhamento de barra da suplementação (um caso; 2,8%). CONCLUSÕES: Com melhora de parâmetros clínicos e radiológicos, a técnica se mostrou segura e eficaz no tratamento de condições degenerativas da coluna lombar.

Manejo de la migración posterior de los dispositivos intersomáticos colocados por vía posterior (PLIF): análisis bibliográfico

OBJETIVO: Se tiene la finalidad de presentar el cuadro clínico de tres casos de esta complicación y analizar metodológicamente los trabajos existentes en la bibliografía. MÉTODO: Tres pacientes operados de columna lumbar a quienes se les realizó una artrodesis circunferencial y que presentaron en el posoperatorio, después de bastante tiempo, nueva sintomatología relacionada con la migración de uno o de los dos PLIF. RESULTADOS: Se realizó mediante el abordaje por vía anterior retroperitoneal, para disectomía, retiro de material migrado y colocación de un dispositivo intersomático anterior. En el primer caso se asoció un abordaje posterior para el retiro del material de osteosíntesis. Se realizó una búsqueda bibliográfica para analizar los datos sobre el retiro según parámetros de evidencia científica. CONCLUSIONES: No existen publicaciones de Evidencia tipo 1 o 2 que marquen directivas claras. La presencia de fibrosis posquirúrgica orientaría al abordaje por vía anterior en el retiro de los dispositivos intersomáticos y así evitaría las lesiones del saco dural y la elongación radicular. La dificultad del manejo vascular y el riesgo de eyaculación retrógrada en pacientes del sexo masculino son parámetros a tener en cuenta para optar por el abordaje posterior. El retiro de los PLIF migrados a posterior, que causen sintomatología dolorosa y/o deficitaria, se convierte en una práctica altamente exigente y de manejo dificultoso.

Examining risk factors for posterior migration of fusion cages following transforaminal lumbar interbody fusion: a possible limitation of unilateral pedicle screw fixation

Object

Because the authors encountered 4 cases of hardware migration following transforaminal lumbar interbody fusion, a retrospective study was conducted to identify factors influencing the posterior migration of fusion cages.

Methods

Patients with lumbar degenerative disc disease (125 individuals; 144 disc levels) were treated using transforaminal lumbar interbody fusion and followed for 12–33 months. Medical records and pre- and postoperative radiographs were reviewed, and factors influencing the incidence of cage migration were analyzed.

Results

Postoperative cage migration was found in 4 patients at or before 3 months. Because all the cages that migrated postoperatively were bullet-shaped (Capstone), only these cages were analyzed. The analysis of preoperative radiographs revealed that higher posterior disc height ([PDH] ≥ 6 mm) significantly increased the incidence of postoperative cage migration, but percent slippage, translation, range of motion, and Cobb angle did not. The incidence of cage migration in patients with unilateral fixation (3 [8.3%] of 36) was not significantly different from that in patients with bilateral fixation (1 [2.1%] of 48). Patients who had scoliotic curvature with a Cobb angle > 10° when treated with unilateral fixation demonstrated a tendency to have more frequent postoperative cage migration than patients treated with bilateral fixation.

To examine the influence of the height of fusion cages, a value obtained by subtracting preoperative anterior disc height (ADH) or PDH from cage height was defined as “Cage height – ADH” (or “Cage height –PDH”). The analysis revealed that the value for “Cage height –ADH” as well as “Cage height –PDH” was significantly lower in migrated levels than in nonmigrated levels, suggesting that the choice of undersized cages may increase the incidence of cage migration.

Conclusions

The results suggest that the use of a bullet-shaped cage, higher PDH, the presence of scoliotic curvature, and undersized fusion cages are possible risk factors for cage migration. One patient with postoperative cage migration following bilateral screw fixation underwent revision surgery, and the pedicle screw fixation was found to be disrupted. Other than in this patient, cage migration occurred only in those treated by unilateral fixation. The potential for postoperative cage migration and limitations of unilateral fixation should be considered by spine surgeons.

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.

Early outcomes and safety of the minimally invasive, lateral retroperitoneal transpsoas approach for adult degenerative scoliosis

Object

The object of this study was to evaluate an alternative surgical approach to degenerative thoracolumbar deformity in adults. The authors present their early experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placing interbody grafts and providing anterior column support for adult degenerative deformity.

Methods

The authors retrospectively reviewed a prospectively acquired database of all patients with adult thoracolumbar degenerative deformity treated with the minimally invasive, lateral retroperitoneal transpsoas approach at our institution. All patient data were recorded including demographics, preoperative evaluation, procedure used, postoperative follow-up, operative time, blood loss, length of hospital stay, and complications. The Oswestry Disability Index and visual analog scale (for pain) were also administered pre- and postoperatively as early outcome measures. All patients were scheduled for follow-up postoperatively at weeks 2, 6, 12, and 24, and at 1 year.

Results

The authors identified 25 patients with adult degenerative deformity who were treated using the minimally invasive, lateral retroperitoneal transpsoas approach. All patients underwent discectomy and lateral interbody graft placement for anterior column support and interbody fusion. The mean total blood loss was 53 ml per level. The average length of stay in the hospital was 6.2 days. Mean follow-up was 11 months (range 3–20 months). A mean improvement of 5.7 points on visual analog scale scores and 23.7% on the Oswestry Disability Index was observed. Perioperative complications include 1 patient with rhabdomyolysis requiring temporary hemodialysis, 1 patient with subsidence, and 1 patient with hardware failure. Three patients (12%) experienced transient postoperative anterior thigh numbness, ipsilateral to the side of approach. In this series, 20 patients (80%) were identified who had more than 6 months of follow-up and radiographic evidence of fusion. The minimally invasive, lateral retroperitoneal transpsoas approach, without the use of osteotomies, did not correct the sagittal balance in approximately one-third of the patients.

Conclusions

Degenerative scoliosis of the adult spine is secondary to asymmetrical degeneration of the discs. Surgical decompression and correction of the deformity can be performed from an anterior, posterior, or combined approach. These procedures are often associated with long operative times and a high incidence of complications. The authors' experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placement of a large interbody graft for anterior column support, restoration of disc height, arthrodesis, and realignment is a feasible alternative to these procedures.

Posterior migration of fusion cages in degenerative lumbar disease treated with transforaminal lumbar interbody fusion: a report of three patients

STUDY DESIGN

A case report of 3 patients with posterior migration of bullet-shaped fusion cages after transforaminal lumbar interbody fusion (TLIF). One patient required emergency revision surgery; the other 2 patients are being observed during conservative treatment.

OBJECTIVE

To review cases of posterior migration of fusion cages and report ensuing clinical courses.

SUMMARY OF BACKGROUND DATA

TLIF is a commonly used procedure; however, there are few reports describing cage migration after the procedure. In most cases, when posterior cage migration follows posterior lumbar interbody fusion, emergency revision surgery is required. One recent study reported a case of posterior cage migration after TLIF, which was treated conservatively.

METHODS

Posterior migration of the bullet-shaped fusion cages occurred 1 to 2 months after TLIF in 3 patients. One of the 3 patients had isthmic spondylolisthesis treated by TLIF with bilateral pedicle screw fixation. The other 2 patients had degenerative scoliosis and were treated by TLIF with unilateral pedicle screw fixation.

RESULTS

The patient with isthmic spondylolisthesis required revision surgery because the migrated cage caused nerve root irritation. The migrated cage was removed and a large-sized cage was employed to achieve stability. The other 2 patients had no pathologic symptoms after the posterior migration of the cage and were treated conservatively and observed.

CONCLUSION

Revision surgery after TLIF appears relatively safe because the migrated cage tends to locate more laterally than in patients with cage migration after posterior lumbar interbody fusion. Cage migration subsequent to TLIF may not cause compression of neural tissues, so conservative treatment may suffice for these patients. Unilateral pedicle screw fixation may not provide sufficient stability to prevent cage migration in patients with degenerative scoliosis. Further study is needed to clarify surgical indications for unilateral pedicle screw fixation in TLIF.

Perioperative complications in revision anterior lumbar spine surgery: incidence and risk factors

STUDY DESIGN

This is a retrospective review of 129 consecutive anterior lumbar revision surgeries in 108 patients. It is a single-center, multi-surgeon study.

OBJECTIVE

To determine occurrence rates and risk factors for perioperative complications in revision anterior lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

Although complication rates from large series of primary anterior fusion procedures have been reported, reports of complication rates for revision anterior fusion procedures are relatively rare. Concern exists chiefly about the risk to vascular and visceral structures because of scar tissue formation from the original anterior exposure.

METHODS

This was a retrospective review of 129 consecutive anterior revision lumbar surgeries in 108 patients operated between 1998 and 2003. There were 40 men and 68 women. The age of patients ranged from 25 to 83 (average 50.6 years). Patients were excluded if surgery was for tumor or infection. Patients were divided into 2 groups; those with revision surgery at the same level and those with revision surgery at an adjacent level. Outcome measures included all perioperative complications. Statistical analysis included Student t test and nonparametric sign-rank.

RESULTS

The number of surgical levels treated for revision was similar between the 2 groups (1 level 69%; 2 levels 19%; 3 or more levels 12%). Revision cases at the same operative level had a higher overall complication rate (42%) compared with extensions (20%; P = 0.007). This difference was primarily because of vein lacerations (23.7% vs. 3.6%, P = 0.002). There were 2 ureteral problems, both successfully salvaged. There were no arterial injuries or deaths.

CONCLUSION

Complication rates for revision lumbar surgery in this series were 3 to 5 times higher than reported for primary lumbar exposures. Complication rates were significantly higher for revision anterior lumbar fusions at the same segment, which were typically in the lower lumbar spine, compared with cases involving extensions, which were typically in the upper lumbar spine.

Access strategies for revision in anterior lumbar surgery

STUDY DESIGN

Sixty-two consecutive patients undergoing anterior lumbar revision surgery from February 2000 to September 2007 were evaluated for approach strategies and complications.

OBJECTIVE

To determine the incidence of complications in these patients and to make recommendations on future revisions based on the results obtained.

SUMMARY OF BACKGROUND DATA

Only 2 articles exist in the literature that address this situation and they have widely varying results in a small number of patients. This larger series may help give more certainty to the expectations for complications in patients undergoing revision anterior lumbar surgery.

METHODS

A concurrent database was maintained on these 62 consecutive patients. Preoperative strategies were evaluated and complications were tabulated as they occurred and later analyzed to arrive at recommendations for future similar cases.

RESULTS

Twenty-three patients had the same level revised and 39 patients had adjacent levels operated on. There were 3 venous injuries (4.8%), 3 arterial injuries (4.8%), and 1 ureteral injury (1.6%). All 3 arterial injuries occurred while approaching L3-L4 after L4 to S1 prior fusion or disc replacement. All 3 venous injuries and the ureteral injury occurred while approaching a previously operated level or levels. Six of these patients had the injuries repaired and the procedures completed with full recovery. One L5-S1 revision had the procedure aborted after a venous injury. There were no deaths.

CONCLUSION

Although the incidence of complications in revisions is much greater than for index cases, the actual percentage of venous, arterial, and ureteral complications is certainly acceptable for patients who must have this type of surgery. Only very experienced access surgeons should attempt revision surgery.

Implications of lumbar plexus anatomy for removal of total disc replacements through a posterior approach

STUDY DESIGN

An anatomic study in which the lumbar plexuses of 14 embalmed cadavers were dissected bilaterally and measured using a posterior approach.

OBJECTIVE

To determine the cephalocaudal (root-to-root) distances and the mediolateral (root-to-tether) distances within the lumbar plexus and determine the feasibility for removal of a lumbar total disc replacement (TDR) through these anatomic spaces using a posterior approach.

SUMMARY OF BACKGROUND DATA

Currently, lumbar TDRs are implanted primarily through an anterior retroperitoneal or transperitoneal approach. However, revision surgeries through these approaches can be complicated by significant adhesions, with potential injuries to intra- and retroperitoneal contents. Advancements in accessing anterior column structures through a posterior lumbar extracavitary approach suggest that posterior removal of TDRs may be an alternative. Unlike the thoracic extracavitary approach in which ligation of the thoracic nerve rarely leaves significant morbidity, the lumbar extracavitary approach cannot rely on the analogous ligation of the lumbar root to achieve access. Therefore, feasibility of the lumbar extracavitary approach depends on the presence of sufficient anatomic space between the tethered nerves of the lumbar plexus.

METHODS

Fourteen adult cadavers (5 M/9F) were dissected through a posterior approach to expose the lumbar plexus bilaterally. The root-to-root distances at levels L2-S1 and corresponding root-to-tether distances at levels L3-L5 were measured bilaterally.

RESULTS

Root-to-root distance was smallest at the male L5-S1 interval (11.7 +/- standard deviations 4.1 mm). Root-to-tether distance was smallest at the female L5 (43.1 +/- standard deviations 8.4 mm). These plexus measurements compare favorably with the CHARITE TDR components, in which the thickest sliding core is 11.0 mm in height and the largest endplate is 42.0 mm in width.

CONCLUSION

This anatomic study suggests that posterior TDR removal is possible in the lumbar spine without undue risk to the surrounding nervous structures.