Minimum 2-year analysis of sacropelvic fixation and L5-S1 fusion using S1 and iliac screws

Etiology and revision surgical strategies in failed lumbosacral fixation of adult spinal deformity constructs

STUDY DESIGN

Retrospective case analysis.

OBJECTIVE

The purpose of this study was to evaluate the etiology and salvage strategies of failed lumbosacral fixation in adult spinal deformity patients.

SUMMARY OF BACKGROUND DATA

When extending a long spinal deformity fusion to the sacrum, the lumbosacral junction is a common site for implant problems and pseudarthrosis.

METHODS

Clinical and radiographic results of 33 patients (26 women/seven men; average age, 53.5 years; range, 21-73) diagnosed and treated for lumbosacral fixation failure between 1995 and 2007 were reviewed. Twenty-one of the 33 patients underwent revision surgery at one institution for these failures and were followed postoperatively for more than 2 years (average, 50.7 months).

RESULTS

Twenty-nine of these 33 patients had two sacral screws, two patients one sacral screw, and two patients none. Bicortical sacral screws were placed in 18 patients, only 12 had distal fixation to the sacral screws (bilateral iliac screws, n = 9; others, n = 3). Seventeen of 19 patients without distal fixation to the sacral screws had screw loosening/pullout at L5 or S1. Anteriorly at L5-S1: 4/6 bone grafts collapsed, 5 of 15 intervertebral discs without anterior column support collapsed, and two of 12 titanium cages subsided into the endplates. Rod breakage between L5 and S1 (n = 9) was seen only in patients with distal fixation to the sacral screws. Nineteen of 21 revision patients received two bicortical sacral screws, whereas 20 received distal fixation to the sacral screws consisting of bilateral iliac screws in 16. Nineteen patients received anterior column support at L5-S1. Fifteen of 21 revision patients achieved solid fusion at ultimate follow-up; however, six had additional rod breakage or dislodgement at the lumbosacral junction.

CONCLUSION

With long fusions to the sacrum in the treatment of spinal deformity, the use of bilateral S1 screws alone may allow for screw loosening/pullout and/or L5-S1 cage/graft collapse/subsidence. Adding bilateral iliac screws and an anterior structural cage/graft at L5-S1 will protect the S1 screws, but may still allow L5-S1 rod breakage/dislodgement because of lumbosacral pseudarthrosis. Revision surgery in these patients remains a challenge.

Bilateral pars fractures complicating long fusion to L5 in a patient with rheumatoid arthritis

STUDY DESIGN

Case report.

OBJECTIVE

To report bilateral pars fractures at L5 complicating a long fusion for adult idiopathic scoliosis in a patient with rheumatoid arthritis.

SUMMARY OF BACKGROUND DATA

To our knowledge, there are no reports in the literature regarding bilateral pars fractures at the end instrumented vertebrae of a long fusion at the lumbosacral junction, nor reports that have evaluated long spinal deformity corrections in patients with rheumatoid arthritis. The question of ending a long fusion at L5 or S1 is controversial, and a review is presented.

METHODS

We present the patient's history, physical examination, and radiographic findings; describe the surgical treatment and long-term follow-up; and provide a literature review.

RESULTS

Bilateral pars fractures at the end instrumented vertebrae of a long construct (T4-L5) that we discovered were subsequently revised by extension of the fusion to the sacrum. Anterior structural support at L5-S1 was also provided. At the latest follow-up (46 months), the patient has had no recurrence of her symptoms. Her radiographs showed a stable construct without loss of alignment in the sagittal or coronal planes. Her rheumatoid arthritis continues to be treated with biologic, disease-modifying antirheumatic drugs.

CONCLUSION

To our knowledge, this is the first report of the treatment and long-term outcome of a patient with rheumatoid arthritis and bilateral pars fractures at the end instrumented vertebrae (L5) of a long deformity correction construct.

The flying buttress construct for posterior spinopelvic fixation: a technical note

Background

Posterior fusion of the spine to the pelvis in paediatric and adult spinal deformity is still challenging. Especially assembling of the posterior rod construct to the iliac screw is considered technically difficult. A variety of spinopelvic fixation techniques have been developed. However, extreme bending of the longitudinal rods or the use of 90-degree lateral offset connectors proved to be difficult, because the angle between the rod and the iliac screw varies from patient to patient.

Methods

We adopted a new spinopelvic fixation system, in which iliac screws are side-to-side connected to the posterior thoracolumbar rod construct, independent of the angle between the rod and the iliac screw. Open angled parallel connectors are used to connect short iliac rods from the posterior rod construct to the iliac screws at both sides. The construct resembles in form and function an architectural Flying Buttress, or lateral support arches, used in Gothic cathedrals.

Results and discussion

Three different cases that illustrate the Flying Buttress construct for spinopelvic fixation are reported here with the clinical details, radiographic findings and surgical technique used.

Conclusion

The Flying Buttress construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein coronal or sagittal balance cannot be achieved, for example in cases with significant residual pelvic obliquity, or in revision spinal surgery for failed lumbosacral fusion.

Biomechanical testing of a concept of posterior pelvic reconstruction in rotationally and vertically unstable fractures

The purpose of this study was to assess the stability of a developmental pelvic reconstruction system which extends the concept of triangular osteosynthesis with fixation anterior to the lumbosacral pivot point. An unstable Tile type-C fracture, associated with a sacral transforaminal fracture, was created in synthetic pelves. The new concept was compared with three other constructs, including bilateral iliosacral screws, a tension band plate and a combined plate with screws. The pubic symphysis was plated in all cases. The pelvic ring was loaded to simulate single-stance posture in a cyclical manner until failure, defined as a displacement of 2 mm or 2°. The screws were the weakest construct, failing with a load of 50 N after 400 cycles, with maximal translation in the craniocaudal axis of 12 mm. A tension band plate resisted greater load but failure occurred at 100 N, with maximal rotational displacement around the mediolateral axis of 2.3°.

The combination of a plate and screws led to an improvement in stability at the 100 N load level, but rotational failure still occurred around the mediolateral axis. The pelvic reconstruction system was the most stable construct, with a maximal displacement of 2.1° of rotation around the mediolateral axis at a load of 500 N.

Sacropelvic fixation: techniques and complications

STUDY DESIGN

Literature-based topic review.

OBJECTIVE

To review the indications and techniques for different sacropelvic fixation methods and to outline important associated complications.

SUMMARY OF BACKGROUND DATA

Despite all the advances and new developments in spinal instrumentation techniques, fixation at the lumbosacral junction continues to be one of the important challenges to spine surgeons. The poor bone quality of the sacrum, the complex regional anatomy, and the tremendous biomechanical forces at the lumbosacral junction contribute to the high rates of instrumentation-related problems. Although many techniques for sacropelvic fixation have been attempted, only a few are still widely used because of the high rate of complications associated with some of those techniques.

METHODS

Review of literature and expert opinion.

CONCLUSION

There are many indications for sacropelvic fixation. Long fusions to the sacrum are the most common reasons for extending the instrumentation to the pelvis. Spinal surgeons performing complex spinal reconstruction should be familiar with the currently available techniques, including their potential risks and complications. Surgical treatment decisions should be based on an individual patient's anatomy and abnormalities, and on the surgeon's experience.

A mid-term follow-up result of spinopelvic fixation using iliac screws for lumbosacral fusion

OBJECTIVE

Iliac screw fixation has been used to prevent premature loosening of sacral fixation and to provide more rigid fixation of the sacropelvic unit. We describe our technique for iliac screw placement and review our experience with this technique.

METHODS

Thirteen consecutive patients who underwent spinopelvic fixation using iliac screws were enrolled. The indications for spinopelvic fixation included long segment fusions for spinal deformity and post-operative flat-back syndrome, symptomatic pseudoarthrosis of previous lumbosacral fusions, high-grade lumbosacral spondylolisthesis, lumbosacral tumors, and sacral fractures. Radiographic outcomes were assessed using plain radiographs, and computed tomographic scans. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and questionnaire about buttock pain.

RESULTS

The median follow-up period was 33 months (range, 13-54 months). Radiographic fusion across the lumbosacral junction was obtained in all 13 patients. The average pre- and post-operative ODI scores were 40.0 and 17.5, respectively. The questionnaire for buttock pain revealed the following: 9 patients (69%) perceived improvement; 3 patients (23%) reported no change; and 1 patient (7.6%) had aggravation of pain. Two patients complained of prominence of the iliac hardware. The complications included one violation of the greater sciatic notch and one deep wound infection.

CONCLUSION

Iliac screw fixation is a safe and valuable technique that provides added structural support to S1 screws in long-segment spinal fusions. Iliac screw fixation is an extensive surgical procedure with potential complications, but high success rates can be achieved when it is performed systematically and in appropriately selected patients.

Reduction and transforaminal lumbar interbody fusion with posterior fixation versus transsacral cage fusion in situ with posterior fixation in the treatment of Grade 2 adult isthmic spondylolisthesis in the lumbosacral spine

OBJECT

In situ transsacral fusion in the treatment of low-grade isthmic spondylolisthesis has rarely been reported. The authors treated 13 cases of L-5 Grade 2 isthmic spondylolisthesis associated with collapsed disc space and osteoporosis by using transsacral fusion and fixation, and compared its clinical and radiological outcomes with the results of transforaminal lumbar interbody fusion (TLIF) and instrumental reduction in 21 patients.

METHODS

The authors retrospectively analyzed 21 patients in Group A who were treated with reduction and TLIF, and 13 patients in Group B who were treated with transsacral cage fusion. Oswestry Disability Index and visual analog scale scores of back and leg pain were used to evaluate clinical outcomes. Radiological parameters for assessment included the percentage of slippage, whole lumbar lordosis, and lumbosacral angle. Operative data, fusion rate, and perioperative complications were recorded as well.

RESULTS

The mean operation time and blood loss in Group B was less than that in Group A. Both groups realized good recovery from previous symptoms. The decrease in back and leg pain after surgery was significant within each group, without much difference between the 2 groups. No significant differences were found in lumbosacral angle, whole lumbar lordosis, visual analog scale score, and Oswestry Disability Index score between the 2 groups after surgery. The solid fusion rate was 95.2% in Group A and 92.3% in Group B. In Group A, 2 patients suffered from graft site pain, 1 had a superficial infection, and 1 had screw loosening; in Group B, dural tears were found in 2 patients, transient S-1 paresthesia in 2, and extensor hallucis longus muscle weakness in 1.

CONCLUSIONS

For patients with a collapsed disc space and poor bone quality, posterior in situ transsacral cage fusion may be used as an alternative to the TLIF procedure. The short-term clinical and radiological outcomes in the transsacral cage group were comparable with those in the TLIF group, although with a relatively higher neurological complication rate.

Low profile pelvic fixation with the sacral alar iliac technique in the pediatric population improves results at two-year minimum follow-up

STUDY DESIGN

Retrospective review.

OBJECTIVE

Anchor stability and prominence are problems with pelvic fixation in pediatric spinal deformity surgery. We compared the new sacral alar iliac (SAI) fixation technique (with a starting point in the sacral ala and in-line anchors deep under the midline muscle flap) with other methods of screw fixation.

SUMMARY OF BACKGROUND DATA

Iliac anchors have been shown to provide the best form of pelvic fixation. A trajectory from the posterior sacral surface to the iliac wings has recently been described. To our knowledge, no clinical series has compared this method of pelvic fixation in children to others.

METHODS

Of 32 consecutive pediatric patients who underwent SAI fixation, 2 died and 26 returned for follow-up (>2 years). Mean age at surgery was 14 years. Average screw size was 67 mm long and 7 to 9 mm in diameter. Clinical examinations, radiographs, and computed tomography scans were analyzed. Outcomes included pain over the implants, screw placement, implant prominence, radiographic lucency, need for revision, and infection. SAI patients were compared with 27 previous patients who had pelvic fixation via other screw techniques.

RESULTS

For SAI fixation, correction of pelvic obliquity and Cobb angles were 20° ± 11° (70%) and 42° ± 25° (67%), respectively. For other pelvic fixation methods, those values were 10° ± 9° (50%), and 46° ± 16° (60%), respectively. Compared with other screws, SAI screws provided significantly better pelvic obliquity correction (P = 0.002) but no difference in Cobb correction. There were 2 lucencies adjacent to screws in both groups. Computed tomography scans of 18 SAI patients showed no intrapelvic protrusion, but 1 screw extended laterally (<5 mm). One early SAI patient required revision with larger screws, which relieved pain; there was 1 revision in the comparison group. SAI patients had no deep infections, implant prominence, late skin breakdown, or anchor migration; traditional patients had 3 deep infections (P = 0.09) and 3 instances of implant prominence, skin breakdown, or anchor migration.

CONCLUSION

SAI pelvic fixation produces better correction of pelvic obliquity than do previous techniques. Radiographic and clinical anchor stability is satisfactory at 2-year follow-up.

Three-dimensional image-guided placement of S2 alar screws to adjunct or salvage lumbosacral fixation

BACKGROUND CONTEXT

Achieving fusion across the lumbosacral junction is challenging because of the unfavorable biomechanics associated with ending a fusion at this level. Bicortical placement of S1 pedicle screws can increase the construct stability at the lumbosacral junction; however, construct failure and pseudoarthrosis can still result. Iliac screws have been shown to increase the stiffness of lumbosacral constructs, but disadvantages include difficulty in connecting the iliac screw to adjacent sacral screws, painful screw loosening or prominence requiring removal, and the inability to place the screws in some patients with previous iliac crest autograft harvest.

PURPOSE

The purpose of the study is to describe a technique of S2 alar screw placement using three-dimensional image guidance.

STUDY DESIGN/SETTING

The study design is a retrospective analysis.

PATIENT SAMPLE

Twenty patients undergoing lumbosacral fusion had 32 screws placed using this technique.

OUTCOME MEASURES

An independent radiologist graded screw placement and lumbosacral fusion on thin-cut postoperative computed tomographic (CT) scans.

METHODS

Image guidance in this study was accomplished with the Medtronic Stealth Station Treon (Medtronic Inc., Littleton, MA, USA) used in conjunction with the O-ARM (Medtronic Inc.). Indications for placement of S2 alar screws included the following: to adjunct S1 pedicle screws in multilevel fusion cases; as an adjunct or alternative to S1 pedicle screws in pseudoarthrosis revision cases in which the S1 screws had loosened; as an alternative to S1 pedicle screws in cases where medial trajectory of an S1 pedicle screw was difficult to obtain because of a low-set lumbosacral junction; and a combination of the above. The entry point of the screw was typically chosen lateral and superior to the S2 dorsal foramen with the trajectory directed anterior, inferior, and lateral. Attempt was made to place the screw with the tip purchasing, but not penetrating through, the triangular area of cortical bone that can be found at the anterior, inferior, and lateral boundary of the sacral ala. An independent radiologist graded the placement of the screws on the intraoperative CT scan obtained with the O-ARM or on postoperative CT scans. Lumbosacral fusion was assessed on postoperative CT scans obtained at follow-up.

RESULTS

No complications occurred in this study as a result of S2 alar screw placement or image guidance. Five screws did penetrate the anterior cortex of the sacrum, with no clinical consequence. At the time of abstract submission, 16 patients were able to have follow-up CT scans, 15 of which were graded as solid fusion at the lumbosacral junction by the grading radiologist.

CONCLUSIONS

Three-dimensional image guidance allows for safe placement of large S2 sacral alar screws that can provide additional biomechanical stability to lumbosacral constructs or serve as an alternate point of sacral fixation when S1 pedicle screws cannot be salvaged or placed in a medial trajectory.

Adult degenerative scoliosis: evaluation and management

Degenerative scoliosis is a prevalent issue among the aging population. Controversy remains over the role of surgical intervention in patients with this disease. The authors discuss a suitable approach to help guide surgical treatment, including decompression, instrumented posterior spinal fusion, anterior spinal fusion, and osteotomy. These treatment options are based on clinical analysis, radiographic analysis of the mechanical stability of the deformity, given pain generators, and necessary sagittal balance. The high potential complication rates appear to be outweighed by the eventual successful clinical outcomes in patients suitable for operative intervention. This approach has had favorable outcomes and could help resolve the controversy.

Critical length of fusion requiring additional fixation to prevent nonunion of the lumbosacral junction

STUDY DESIGN

A retrospective study.

OBJECTIVE

To determine the critical length of fusion that warrants additional stronger fixation in lumbosacral (L-S) fusion, and to analyze the risk factors of nonunion at the L-S junction.

SUMMARY OF BACKGROUND DATA

Long lever arm fusion down to S1 requires stronger fixation than short lever arm fusion. However, no published criteria are available about the critical length of fusion requiring stronger fixation to the ilium or S2 to obtain adequate stability for union at the L-S junction.

METHODS

A total of 327 adult patients with degenerative lumbar disease, who were treated with instrumented fusion, including the L-S junction, were included in this study. Mean patient age was 59.7 (20-79) years and the minimum follow-up was 12 months. Union rates were compared using univariate and multivariate logistic regression analysis. Length of fusion, age, sex, lumbar lordosis at preoperative, early postoperative and final follow-ups, BMD, smoking history, associated morbidities, fat content of paraspinal muscle, methods of fusion, and levels of intercristal line were examined as independent variables to identify factors that affect union rate at the L-S junction.

RESULTS

Of the 327 patients, 47 (14.4%) had nonunion at the L-S junction. Union rate of the L-S junction at the single level, and at 2, 3, 4, 5, and more than 5 levels were 96.6%, 92.9%, 87.4%, 64.7%, 66.7%, and 58.0%, respectively. A significant difference of union rate was found between less than 4 levels and 4 or more levels of fusion (P < 0.05). The factors found by multivariate analysis to significantly affect union rate at the L-S junction were fusion length and fat content of paraspinal muscle.

CONCLUSION

The risk of nonunion at the L-S junction was found to increase significantly for more than 3 levels of fusion. We advise that additional stronger fixation is needed in such cases.

A biomechanical comparison of different types of lumbopelvic fixation

STUDY DESIGN

Comparative biomechanical testing in calf spines.

OBJECTIVE

To biomechanically evaluate 4 techniques of lumbosacral fixation.

SUMMARY OF BACKGROUND DATA

Pelvic fixation is a problematic area, and currently, the preferred method of pelvic fixation is controversial. Clinically, iliac screws have demonstrated decreased rod breakage rates, and better correction of pelvic obliquity than unthreaded rods (Galveston technique), but several modern methods of iliac fixation have not been compared.

METHODS

A total of 32 male calf spines were tested under axial rotation, flexion/extension, and lateral bending. Following intact testing, specimens were instrumented in the following groups: group 1-Modified Galveston technique with rods connected directly to iliac screws (no S1 fixation); group 2-S1 screws and iliac screws with offset connectors distal to S1; group 3-S1 screws and iliac screws with offset connectors coupled to the longitudinal rod between L6 and S1; and group 4-S1 and S2 screws without iliac fixation. Pedicle screws were placed from L3 to L6. Following nondestructive testing, specimens were fixed at the cephalad aspect of the construct and flexed to failure, with peak failure moment (Nm).

RESULTS

Group 1 demonstrated significantly more flexion/extension than groups 2, 3, 4 (P<0.001). There were no significant differences between groups for lateral bending or axial rotation at L3-S1 or L6-S1. During destructive testing, group 4 showed a significant reduction in peak failure compared to group 1 (P<0.001), group 2 (P=0.001), and group 3 (P<0.001). There was no significant difference between groups 1, 2, and 3 and all specimens failed at the distal fixation.

CONCLUSION

With extension of instrumentation across the lumbosacral junction, our results indicate significant improvement in stability with the use of S1 screws and iliac screw fixation. Furthermore, there does not appear to be any significant difference in the location of the connector for the iliac screw.

Effect of iliac screw insertion depth on the stability and strength of lumbo-iliac fixation constructs: an anatomical and biomechanical study

STUDY DESIGN

Comparison of feasibility and safety of the placement of short and long iliac screws by anatomic and biomechanical evaluations as they apply to lumbo-iliac fixation construct.

OBJECTIVE

To compare the stability of the short and long iliac screw fixations for lumbo-iliac reconstruction by anatomic and biomechanical evaluations.

SUMMARY OF BACKGROUND DATA

Spinopelvic reconstruction remains a challenge to spine surgeons. Despite the advent of many fixation methods, the use of iliac screws seems most favorable so far. Various lengths of iliac screws are applied in surgical treatments; however, no biomechanical comparison has been reported based on the screw length.

METHODS

For anatomic observation, CT scan data of 60 Chinese adults were used to measure the details of the iliac spine structures. For biomechanical evaluation, 7 adult human cadavers (L3-pelvis) were observed. L4-S1 pedicle screw fixation was performed with posterior spinal fixation system. On the basis of the lengths of iliac screws, 2 groups were tested (short screw group using 70 mm screws and long screw group using 138 mm screws). In this study, short and long iliac screws were placed in the same specimen. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 Nm torsion loading modes for stiffness evaluations. Finally, pullout testing was performed for all the iliac screws to measure the maximum pullout force.

RESULTS

The length of the line between posterior superior iliac spine and anterior inferior iliac spine was 140.6 +/- 1.1 mm, and the distance between this line and the greater sciatic notch was 18.3 +/- 0.8 mm. The length of the line between posterior superior iliac spine and the second narrowest point was 67.1 +/- 0.62 mm in men and 70.1 +/- 1.4 mm in women. Insertion lengths of the short and long iliac screws were 70 +/- 2 mm and 138 +/- 4 mm, respectively. The lumbo-pelvic reconstruction using short and long iliac screws restored 53.3% +/- 13.6% and 57.6% +/- 16.2% of the initial stiffness in compression testing respectively. In torsion testing, the use of short and long iliac screws harvested 55.1% +/- 11.9% and 62.5% +/- 9.2% of the initial stiffness, respectively. No significant difference was detected between the 2 reconstructions in terms of compressive and torsional stiffness (P > 0.05). However, the maximum pullout strength of long iliac screw group was significantly higher than the short screw group (P < 0.05).

CONCLUSION

The local stability is rather difficult to be restored to the original levels regardless the length of iliac screws. Obviously, long iliac screws resisted significantly greater axial pullout force. However, under physiologic, torsional, and compressive loading conditions, the mechanical stability of lumbo-pelvic fixation construct with short iliac screws was comparable with that of the long ones. Therefore, the use of short iliac screws, which are only about half the length of the long iliac screws, could reduce the implantation risk without significantly compromising on the stability of the construct.

Low profile pelvic fixation: anatomic parameters for sacral alar-iliac fixation versus traditional iliac fixation

STUDY DESIGN

Three-dimensional computed tomography (CT) radiographic analysis.

OBJECTIVE

To describe the parameters for a trajectory through a sacral starting point as a method of pelvic fixation in spinal deformity and to compare this technique with insertion from the posterior superior iliac spine (PSIS).

SUMMARY OF BACKGROUND DATA

Long anchors projecting into the ilium provide optimal pelvic fixation. The traditional starting point in the PSIS requires muscle dissection and connectors or rod bends.

METHODS

Twenty pelvic CTs of mature adolescents were analyzed using InSpace, a three-dimensional CT program, by 2 surgeons. Trajectory with maximal length and width through the sacral ala and iliac wing was obtained through CT imaging plane manipulation. Trajectory and starting-point parameters were measured. Parameters were evaluated and compared for insertion from the PSIS.

RESULTS

Based on the ideal trajectory, the mean starting point in S2 was 25 mm caudal to the superior endplate of S1 and 22 mm lateral to the sacral midline (S2 alar-iliac [S2AI] path). Maximal mean S2AI distance was 105 mm (range, 74-129 mm; SD = 11 mm). Maximal mean length for PSIS insertion was 118 mm (range, 99-147 mm; SD = 13 mm). Mean angulation was 40 degrees (SD = 6 degrees ) laterally in the transverse plane and 39 degrees (SD = 6 degrees ) caudally in the sagittal plane. The mean difference between surgeons in selecting the trajectory was 2 degrees and 1 degrees in the transverse and sagittal plane, respectively. The S2AI pathway traversed 35 mm of sacral ala. The narrowest mean width of the ilium along this path was 12 mm (range, 6-18 mm). The starting point for the S2AI was 19 mm deep to the PSIS. The distance from skin for S2AI versus PSIS techniques was 52 and 37 mm, respectively.

CONCLUSION

Iliac fixation through the S2 ala provides a reproducibly chosen starting point in line with S1 pedicle anchors. Implant prominence is minimized because the starting point is 15 mm deeper than the PSIS entry. It is less likely to be affected in cases using iliac crest bone graft harvest because of the more anterior position of the anchor in the ilium.

Ilio-lumbar fixation--the Amrita technique

STUDY DESIGN

Surgical technique description.

OBJECTIVE

To describe a surgical technique of ilio-lumbar fixation with iliac screws, which attempts to overcome some of the current limitations and technical difficulties associated with this surgery.

SUMMARY OF BACKGROUND DATA

The iliac screw technique, which is the most commonly used method of ilio-lumbar fixation, has certain limitations that need special consideration. These include soft tissue coverage, improving the strength of distal anchorage, reducing hardware prominence, avoiding complex 3-dimensional rod contouring, preventing neurologic injury, and acetabular violation.

MATERIALS AND RESULTS

Over the past 5 years, we have used our technique in 8 patients (4 sacral tumors, 2 fracture dislocations, and 2 spinal tuberculosis). In 6 cases, the sacrum was not available for anchoring and hence was bypassed. The follow-up ranged from 3 to 54 months, and 5 patients had resumed normal activities. In 7 cases, the wound healed primarily and the solitary wound failure was in a previously irradiated skin. Other complications like neurologic deficit secondary to the procedure, acetabular violation, and implant failure were not encountered.

CONCLUSIONS

Our technique of ilio-lumbar fixation provides a stable and simple alternative to reconstruct potentially devastating instability of the lumbosacral junction. The 2 iliac screws, when used as described, make the procedure technically easier, reduce the hardware prominence without compromising the stability to construct and provide adequate bone graft.

Results and morbidity in a consecutive series of patients undergoing spinal fusion with iliac screws for neuromuscular scoliosis

We performed a retrospective review study to evaluate the safety and efficacy of iliac screws as a method of pelvic fixation in neuromuscular spinal deformity. All patients with the diagnosis of neuromuscular scoliosis operatively managed with iliac screws undergoing posterior spinal fusion were retrospectively identified over a 32-month period, from December 2002 to August 2005. Evaluation was done for correction of deformity, progression, instrumentation failure, and complications. Progression was defined as an increase in Cobb angle >5 degrees . Of the 14 eligible patients, 12 (86%) had adequate follow-up, with an average final follow-up of 19.5 months (range, 12-39 months). Average patient age at surgery was 15 years. Average number of instrumented levels was 16, with the most common levels being from the second thoracic vertebrae to the sacrum (11/12). A significant correction of deformity from a mean preoperative 66.5 to a mean postoperative 22.8 was achieved. Average postoperative L5-S1 angle was 31 degrees and L1-S1 angle was 61 degrees. At final follow-up, the average L5-S1 angle was 26 degrees and L1-S1 angle was 59 degrees < neither a statistically significant progression (P=.70 and P=.30, respectively). The maximum measured progression was 16 degrees for L5-S1 and 12 degrees for L1-S1. There were no incidences of rod breakage, and there was 1 iliac screw offset connector dislodgement from the rod, which did not require revision. There were no intraoperative complications. There were 3 postoperative wound infections, which required irrigation and debridement and eventually resulted in fusion. In conclusion, this is one of the largest reports of iliac screw use in the correction of neuromuscular scoliosis. In our series we were able to correct the deformity and maintain the lumbar lordosis without progression or failure with a relatively low complication rate.

Corrective osteotomies in spine surgery

Spinal deformities can result in increasing thoracic kyphosis or loss of lumbar lordosis, leading to imbalance in the sagittal plane. Such deformities can be functionally and psychologically debilitating. The Smith-Petersen osteotomy can achieve approximately 10 degrees of correction in the sagittal plane at each spinal level at which it is performed. This osteotomy is beneficial for patients who have a degenerative imbalance in the sagittal plane. The pedicle subtraction osteotomy can achieve approximately 30 degrees to 40 degrees of correction in the sagittal plane at each spinal level at which it is performed. It is the preferred osteotomy for patients with ankylosing spondylitis who have an imbalance of the spine in the sagittal plane. The cervical extension osteotomy is performed in the cervical spine, at the cervicothoracic junction, in patients who have a cervical flexion deformity that impedes their ability to look straight ahead while walking or who have difficulty swallowing. The vertebral column resection is used when the imbalance is severe enough that the other osteotomies cannot correct the deformity, especially in patients who have a combined sagittal and coronal spinal imbalance. Neurologic problems, whether transient or permanent, are the most commonly encountered complications following these procedures. Recent results have shown a high patient satisfaction rate and good functional outcomes after spinal osteotomies done to treat a variety of disorders.

Unilateral and bilateral sacropelvic fixation result in similar construct biomechanics

STUDY DESIGN

In vitro biomechanical investigation of lumbosacropelvic spinal instrumentation.

OBJECTIVE

Determine whether unilateral iliac fixation, with or without an L6 to S1 interbody graft, provides equivalent biomechanical stability compared with bilateral iliac fixation.

SUMMARY OF BACKGROUND DATA

Recent clinical evidence has shown improved clinical outcomes of unilateral iliac fixation compared with bilateral instrumentation that contradicts biomechanical data supporting bilateral instrumentation, although no specific investigation has compared unilateral versus bilateral instrumentation.

METHODS

Sixteen porcine spines were instrumented with bilateral segmental pedicle screws from L1 to S1 and 5.5-mm titanium rods. Spines were randomized to either have an intact L6 to S1 disc space (n = 8/group) or a full discectomy and intervertebral cage at L6 to S1 (n = 8/group). Four reflective noncolinear markers were attached to both L6 and S1. Spines were tested with bilateral ilium, unilateral ilium, and sacrum-only fixation in flexion, extension, lateral bending, and axial torsion between +/-7.0 Nm. L6 to S1 range of motion (degrees) and mechanical stiffness (Nmm/degrees) were compared between groups with a 2-way analysis of variance (P < 0.05).

RESULTS

No significant differences were found in construct stiffness or L6 to S1 motion between unilateral or bilateral fixation for any test direction and both demonstrated significantly less L6 to S1 motion compared with sacrum-only fixation for all tests (all P values <0.005). Bilateral fixation was significantly stiffer than sacrum-only fixation in flexion and extension (P < 0.0001). The interbody cage significantly decreased construct stiffness in extension, lateral bending, and axial torsion (P < 0.002), and significantly increased L6 to S1 motion in torsion compared with an intact disc (P < 0.03).

CONCLUSION

There were no biomechanical differences between bilateral and unilateral iliac screw fixation. Intervertebral cage with full discectomy was significantly less stiff than intact. This study provides biomechanical data to correlate with improved clinical outcomes using unilateral iliac screw fixation, and evidence contraindicating full discectomy with intervertebral cage placement.

ADULT DEGENERATIVE SCOLIOSIS

OBJECTIVE

To review and define principles and features of treatment for adult degenerative scoliosis, the most common cause of adult spinal deformities.

STUDY DESIGN

We conducted a comprehensive review of the literature and our clinical experience.

METHODS

A systematic review of Medline was conducted, including journal articles published in March 2007 and before. We searched for articles related to adult spinal deformities (scoliosis) and treatments.

CONCLUSION

Degenerative scoliosis is a complex disorder. The primary surgical aims are to decompress the neural elements, normalize both sagittal balance and coronal and rotational deformity, fixate to the sacrum/ilium when appropriate, and optimize conditions for osteogenesis and fusion.

LONG-SEGMENT SPINAL FIXATION USING PELVIC SCREWS

OBJECTIVE

Long spinal constructs that extend to the sacrum place added stress on sacral screws. To prevent premature loosening of sacral fixation in these cases, the addition of pelvic screw (iliac screw) fixation has gained in popularity. Pelvic screw fixation has also been used in cases where sacral screw fixation is not possible (e.g., in sacral tumors). Pelvic screw fixation is more straightforward than prior pelvic rod fixation techniques (e.g., the Galveston technique). We describe our technique for pelvic screw fixation and review our experience with this technique.

METHODS

Twenty consecutive patients who underwent spinal-pelvic fixation were followed over a 3-year period (2004–2007). The patient population consisted of 11 men and 9 women with an average age of 58.8 years. Indications for spinal-pelvic fixation in this series included kyphoscoliosis, lumbosacral pseudoarthrosis, sacral fractures, lumbosacral spondylolisthesis, sacral tumors, and lumbar osteomyelitic fractures. Radiographic outcomes were assessed using flexion-extension x-rays and computed tomographic scans. Clinical outcomes were assessed using Odom's criteria and modified Prolo scale.

RESULTS

One patient was lost to radiographic follow-up. One patient died after surgery. The mean follow-up for the remaining patients was 13 months (range, 1–21 mo). Odom's outcomes were rated as good to excellent in 11 (58%), fair in 7 (37%), and poor in 1 (5%) (one patient died). Preoperative and postoperative modified Prolo scores were 10.4 and 12.9, respectively (mean improvement, 2.5). Radiographic fusion across the lumbosacral junction was obtained in 16 (89%) of the 18 patients with follow-up. One patient required revision of a pelvic screw. There was one infection requiring explantation of hardware.

CONCLUSION

Pelvic screw fixation is a safe and effective technique that provides added structural support to S1 screws in long-segment spinal fusions. Furthermore, pelvic screw fixation provides a distal point of fixation in cases where sacral screw fixation is not possible. The use of polyaxial screws and connectors makes this technique easier than Galveston rod fixation of the pelvis.

Revision of loosened iliac screws: a biomechanical study of longer and bigger screws

STUDY DESIGN

The present study compared the biomechanics of 2 revision iliac screws: longer and bigger screws, on human cadaveric pelves.

OBJECTIVE

To determine if a bigger screw resists loosening under cyclic loading better than a longer screw in revising loosened iliac screws.

SUMMARY OF BACKGROUND DATA

Iliac screws have been used in treating spinal deformity, spondylolisthesis and many other spinal diseases. Because of the cancellous bone along the screw trajectory, screw loosening over cyclic loading has been experienced in clinical applications. Two popular revision choices are: a longer screw and a bigger screw. However, their biomechanics has not been characterized. The objective of this study is to determine the rate of loosening of longer or larger revision iliac screws under cyclic loading.

METHODS

Eight pairs of human cadaver pelves were harvested. Each side was randomly assigned for a longer revision screw or a larger revision screw. Because of different bone quality in each specimen, applied load was varied according to the peak insertion torque of the primary iliac screws. The load was applied at an anatomic angle with a frequency of 2 Hz. The motion of screw with respect to the pelvis at the bone entry point was recorded with a motion tracking system. The amount of loosening after a specific number of cycles was determined from the screw motion data.

RESULTS

The average maximal insertion torque of bigger revision screws (3.2 Nm) was greater than that of longer revision screws (2.7 Nm) with P = 0.03. The average loosening rate was 0.28 +/- 0.13 (SE) mm/thousand cycles for longer revision screws and 0.06 +/- 0.05 (SE) mm/thousand cycles for bigger revision screws. The difference between these 2 revision screws was significant (P = 0.03). In addition, the bigger revision screws had a lower loosening rate than that of the primary screws (P = 0.03).

CONCLUSION

Iliac screws are susceptible to loosening under cyclic loading due to the cancellous bone structure surrounding the screw body. Experimental data showed that the bigger revision iliac screw resists loosening better than the longer screw and the primary screw. Thus, the bigger revision screw is favored if the patient's anatomy allows such operation.

Complications in long fusions to the sacrum for adult scoliosis: minimum five-year analysis of fifty patients

STUDY DESIGN

A retrospective study of complications with minimal 5-year follow-up of 50 adults with scoliosis with fusion from T10 or higher to S1.

OBJECTIVES

To document the perioperative and long-term complications and instrumentation problems, and to attempt to determine variables which may influence these problems. It is not a study of curve correction, balance, or functional outcome.

SUMMARY OF BACKGROUND DATA

Several previous studies from this and other centers have shown a relatively high complication rate for this select group of patients. Various fusion techniques (anterior, posterior, autograft, allograft), various instrumentation techniques, and various immobilization techniques have created confusion as to the best methodology to employ. Minimal 2-year follow-ups have been standard, but longer follow-ups have shown additional problems.

METHODS

The study cohort consisted of 50 adult patients from a single center who had undergone corrective scoliosis surgery from T10 or higher to the sacrum and who had at least a 5-year minimum follow-up. The mean age was 54 years (range, 18-72), and the mean follow-up was 9.7 years (range, 5-26). All radiographs, office charts, and hospital charts were combed by an independent investigator for complications, which were divided into major and minor, as well as early, intermediate and late. The curvature values and corrections were the subject of a different article, and were not included in this study.

RESULTS

There were no deaths or spinal cord injuries. Six patients had nerve root complications, 4 of which totally recovered. Pseudarthrosis was seen in 24% of the patients, only 25% of which were detected within the 2-year follow-up period. Pseudarthrosis was most common at the lumbosacral level. There was no statistical difference in the pseudarthrosis rate between patients with sacral-only fixation versus iliac fixation. Painful implants requiring removal were noted in 11 of the 50 patients.

CONCLUSION

Long fusions to the sacrum in adults with scoliosis continue to have a high complication rate. As compared to the original publications in the 1980s (Kostuik and Hall, Spine 1983;8:489-500; Balderston et al, Spine 1986;11:824-9) the more recent articles have shown a reduction, but not elimination of the pseudarthrosis problem using segmental instrumentation and anterior fusion of the lumbar spine coupled with structural interbody grafting at L4-L5 and L5-S1. Two-year follow-up is inadequate as pseudarthrosis and painful implants often are detected later. Only 3 of the 12 patients with pseudarthrosis were detected within the first 2 years after surgery.

Lumbo-sacro-pelvic Fixation Using Iliac Screws for the Complex Lumbo-sacral Fractures

Fractures of lumbo-sacral junction involving bilateral sacral wings are rare. Posterior lumbo-sacral fixation does not always provide with sufficient stability in such cases. Various augmentation techniques including divergent sacral ala screws, S2 pedicle screws and Galveston rods have been reported to improve lumbo-sacral stabilization. Galveston technique using iliac bones would be the best surgical approach especially in patients with bilateral comminuted sacral fractures. However, original Galveston surgery is technically demanding and bending rods into the appropriate alignment is time consuming. We present a patient with unstable lumbo-sacral junction fractures and comminuted U-shaped sacral fractures treated by lumbo-sacro-pelvic fixation using iliac screws and discuss about the advantages of the iliac screws over the rod system of Galveston technique.

Thoracolumbar deformity arthrodesis stopping at L5: fate of the L5-S1 disc, minimum 5-year follow-up

STUDY DESIGN

A retrospective long-term follow-up study.

OBJECTIVE

Evaluate the fate of L5-S1 disc analyzing subsequent disc degeneration and associated risk factors for degeneration at minimum 5-year follow-up (average 9-year follow-up).

SUMMARY OF BACKGROUND DATA

Two previous studies reported the results of long deformity fusions terminating at L5 with minimum 2-year follow-up only.

METHODS

Thirty-one consecutive patients with an average age of 45 years (range, 20-62 years) were fused from the thoracic spine to L5 and were evaluated at a mean follow-up of 9.4 years (range, 5-20.1 year). Patients were evaluated before surgery, after surgery, and latest follow-up with radiographs and Scoliosis Research Society Patient Questionnaire-24 scores. Disc degeneration using validated radiographic Weiner grades. Grade 0 to 1 discs were "healthy" and Grade 2 to 3 were degenerated. Patients with "healthy" discs preoperative that subsequently degenerated were designated subsequent advanced degeneration (SAD).

RESULTS

Two out of 31 patients had preoperative advanced degeneration of the L5-S1 disc (Weiner grade 2-3). Three additional patients had an early revision to the sacrum secondary to sagittal imbalance not thought to be related to SAD. Twenty-six out of 31 patients were assessed as "healthy discs" preoperative (Weiner grade 0-1) and were evaluated for SAD. By latest follow-up, L5-S1 SAD developed in 18 of these 26 patients (69%). Risk factors for the development of SAD included long fusions extending into the upper thoracic spine down to L5 (P = 0.02) and having a circumferential lumbar fusion (P = 0.02). Although preoperative sagittal balance was not significantly different between the "healthy" and SAD group, sagittal balance at follow-up was: C7 plumb >5 cm in 67% of SAD patients and only 13% of "healthy" disc patients (P = 0.009). There was a trend toward inferior Scoliosis Research Society Patient Questionnaire-24 pain scores at follow-up in SAD patients (average score 4.1 vs. 3.4, P = 0.13). Eleven out of 30 patients (35%) had subsequent spinal surgery with 7 of 31 (23%) having extension of their fusion to the sacrum. An additional 6 of 31 (19%) were considered for extension to the sacrum but comorbidities precluded surgery (3 patients) or the patients declined further surgery (3 patients).

CONCLUSION

Advanced L5-S1 DDD developed in 69% of deformity patients after long fusions to L5 with 5 to 15 year follow-up. SAD frequently results in significant positive sagittal balance at a minimum 5-year follow-up. Long fusions to the upper thoracic spine down to L5 and circumferential fusion may further promote subsequent L5-S1 disc degeneration.

Spinopelvic fixation in deformity: a review

Spinopelvic fixation techniques are evolving and now seem to be converging. Good S1 pedicle fixation is the initial key anchor point. The tricortical technique tests out as the best. Supplemental fixation options are available. The most efficacious seems to be iliac fixation, followed by two-level structural interbody support. Achieving appropriate global sagittal balance also lessens the likelihood of implant pullout and places the fusion mass under relatively more compressive forces than tension forces. Regardless of the method of fixation, the ultimate determinant of long-term implant survival is the achievement of adequate biologic fusion.

Iliac screw fixation in neuromuscular scoliosis

STUDY DESIGN

A retrospective review of children with neuromuscular scoliosis treated at our institution with posterior spinal fusion and instrumentation including iliac screws.

OBJECTIVES

To determine the safety and effectiveness of iliac screws in neuromuscular scoliosis constructs.

SUMMARY OF BACKGROUND DATA

The Galveston technique has been a standard method of impacting rods in the iliac wings to provide anchorage for neuromuscular scoliosis constructs. Numerous studies have shown the increased strength of constructs using screws as part of segmental spinal instrumentation. The ideal method of caudal anchorage is still unclear, and the role of iliac screws has yet to be defined.

METHODS

The medical records and radiographs of 50 patients with neuromuscular scoliosis treated with a modified Luque-Galveston posterior spinal fusion and instrumentation technique were reviewed. The instrumentation was anchored to the pelvis via iliac screws: Group A constructs included 2 screws; Group B constructs included 4 screws. The radiographs were analyzed for Cobb angle and pelvic obliquity before surgery and after surgery. Complications were recorded, including infections and implant-related problems.

RESULTS

The average curve correction was 48%. The average pelvic tilt correction was 59%. Complications included 4 deep infections requiring reoperation (8%), 10 screw-related complications (7 in Group A, 3 in the Group B), and 12 non-screw-related implant complications (11 in the Group A, 1 in the Group B).

CONCLUSIONS

The use of screw fixation in the ilium as a means of spinopelvic anchorage is safe and effective in the treatment of neuromuscular scoliosis. The use of 2 screws in each iliac wing provides more stable fixation with fewer implant-related complications than using a single screw.

Long-segment fusion of the thoracolumbar spine in conjunction with a motion-preserving artificial disc replacement: case report and review of the literature

STUDY DESIGN

Case report.

OBJECTIVE

We reviewed the case of a 44-year-old woman who underwent long-segment fusion and an artificial disc replacement.

SUMMARY OF BACKGROUND DATA

There have been many reported advantages and disadvantages of stopping the fusion at L5, with the theoretical benefits being preserved motion, shorter operative time, allowing the remaining disc to compensate for curve correction cephalad in the lumbar spine, and a decreased likelihood for the development of a pseudarthrosis at that distal level.

METHODS

As the issue of the fate of the L5-S1 motion segment continues to be debated, we present the case of a medium-segment thoracolumbar fusion carried down to the L4 stable vertebra, an intervening healthy L4-L5 disc space, with the placement of an artificial disc arthroplasty at the L5-S1 level for a degenerative and discographically positive pain generator.

RESULTS

At 2-year follow-up, her L5-S1 artificial disc replacement level shows 11 degrees range of motion and consolidated fusion from T12 to L4 with complete resolution of her axial back pain. Her T12-L4 construct is stable, and the L4-L5 level is unaffected at the latest follow-up. Her clinical outcome has been excellent with her return to a very active lifestyle.

CONCLUSION

Artificial disc replacement below a long-segment fusion is a viable alternative to performing fusion to additional motion segments.

Partially overlapping limited anterior and posterior instrumentation for adult thoracolumbar and lumbar scoliosis: a description of novel spinal instrumentation, "the hybrid technique"

Progressive and/or painful adult spinal deformity in the thoracolumbar and lumbar spine is sometimes treated surgically by long posterior fusions from the thoracic spine down to the pelvis, especially where there is a major thoracic curve component. Recent advances in anterior spinal instrumentation and spinal surgery technique have demonstrated the improved corrective ability offered by anterior stabilization systems, and the added benefit of limiting the number of vertebral fusion levels required for control of the deformity. The "hybrid technique" is a novel use of anterior instrumentation that applies limited anterior instrumentation down to the low lumbar spine (rods and screws), and partially overlapping short-segment posterior instrumentation to the sacrum (pedicle screws and rods). These constructs avoid posterior thoracic instrumentation and fusions, and avoid extension of posterior instrumentation to the pelvis. In the first 10 patients treated using this technique, thoracolumbar and lumbar major curve correction has averaged 71 and 82% in the immediate postoperative period (n = 7), respectively, and 59 and 68% at 2-year follow-up, respectively. The technique is an appealing and attractive alternative for treatment of thoracolumbar and lumbar scoliosis in the adult population, and avoids the requirement for applying spinal fixation to the thoracic spine and the pelvis.

Degenerative lumbar scoliosis

In adults, symptomatic scoliosis is usually a de novo primary degenerative deformity that develops in the fifth or sixth decade or an unrecognized or untreated idiopathic deformity with superimposed degeneration. The evaluation and treatment of adult scoliosis must focus on addressing patient symptoms while limiting the consequences of the treatment. The presence of neurological deficits, the flexibility of the deformity, the coronal and sagittal balance, and status of spinal segments outside of the main deformity are all important considerations when planning surgery. The complication rate of deformity surgery in adults is potentially high; but excellent functional outcome and patient satisfaction can occur with thorough preoperative patient education and meticulous surgical technique.

Principles for selecting fusion levels in adult spinal deformity with particular attention to lumbar curves and double major curves

STUDY DESIGN

Review article.

OBJECTIVES

To identify decision-making principles for selecting fusion levels in adult spinal deformity, with particular attention to lumbar curves and double major curves.

SUMMARY OF BACKGROUND DATA

Although numerous articles have been published on the selection of fusion levels for adolescent idiopathic scoliosis (AIS) curves, relatively less attention has been paid to the selection of fusion levels for the operative management of adult scoliosis.

METHODS

This is a literature review pertaining to the surgical management of adult scoliosis.

RESULTS

Selection of fusion levels for adult scoliosis can be difficult; however, certain biomechanical and surgical principles can consistently be applied.

CONCLUSION

An appreciation of both the coronal and sagittal plane components of spinal deformity is mandatory to achieve optimal results with surgical stabilization of adult scoliosis.

Progressive junctional kyphosis at the caudal end of lumbar instrumented fusion: etiology, predictors, and treatment

STUDY DESIGN

Clinical case series.

OBJECTIVE

To describe a series of patients with progressive sagittal decompensation caused by failure at the caudal end of an instrumented lumbar fusion.

SUMMARY OF BACKGROUND DATA

Lumbar kyphosis in association with global sagittal decompensation can be a disabling problem, particularly as a late complication of distraction instrumentation. Although kyphosis at the rostral end of instrumented fusions secondary to adjacent segment degeneration has been well described, substantially less has been documented about failure and kyphosis at the caudal end.

METHODS

Patients who have a progressive lumbar kyphosis and sagittal decompensation requiring operative revision were retrospectively reviewed, and radiographic measurements of lumbar lordosis and sagittal balance were performed to study this problem.

RESULTS

There were 13 patients identified. The most common mode of caudal junctional decompensation was related to failure of the most distal fixation. Sagittal decompensation occurred even in the presence of satisfactory lumbar lordosis. Revision surgery and improved sagittal balance were achieved typically using the technique of pedicle subtraction osteotomy and extension of the instrumentation to the sacrum. Osteoporosis, hip osteoarthritis, and substance abuse were commonly observed associations.

CONCLUSIONS

Fixation failure at the caudal end of lumbar-instrumented fusion should be considered in patients with progressive sagittal decompensation. The high potential for failure of L5 pedicle screws after the index surgery warrants serious consideration of extending such fusions into the sacrum/ilium.

Revision Deformity Surgery

Revision deformity surgery may be necessary for several reasons. Symptomatic pseudarthrosis, implant failure or pull-out, or loss of correction may mandate reoperation. The keys to a successful revision procedure are a careful analysis of the problem, particularly the mode of failure and the contributing biomechanical factors, and the development of an appropriate surgical plan.

A proposal for a surgical classification of pediatric lumbosacral spondylolisthesis based on current literature

The classification presented in this paper is the first specifically designed to guide surgical treatment of L5-S1 spondylolisthesis in children and adolescents. It also presents objective criteria to differentiate between low- and high-dysplastic spondylolisthesis and incorporates recent knowledge in the study of sagittal spinopelvic balance. The proposed classification is based on the following: (1) the degree of slip, (2) the degree of dysplasia, and (3) the sagittal spinopelvic balance. To classify a patient, the degree of slip is quantified first to determine if it is low-grade, high-grade, or a spondyloptosis. Then, the degree of dysplasia is evaluated based on seven criteria, in order to separate patients with low- and high-dysplastic spondylolisthesis. Finally, the sagittal spinopelvic balance is assessed from the measurement of the pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT). For low-grade spondylolisthesis, it is classified as low PI/low SS (nutcracker type) or high PI/high SS (shear type). For high-grade spondylolisthesis, it is classified as high SS/low PT (balanced pelvis) or low SS/high PT (retroverted pelvis). Such a comprehensive classification could allow to better evaluate and compare available surgical techniques, and to optimize the treatment of L5-S1 spondylolisthesis. Because the classification was designed so that groups are organized in an ascending order of severity, it becomes easier and more intuitive to develop an associated surgical algorithm because the complexity of the surgery should increase as the severity of the spondylolisthesis increases. A tentative treatment algorithm is proposed but it is not definitive because further studies are required to define the most appropriate treatment for each group.

Minimum 5-year analysis of L5-S1 fusion using sacropelvic fixation (bilateral S1 and iliac screws) for spinal deformity

STUDY DESIGN

Clinical radiographic and outcomes investigation.

OBJECTIVE

To investigate clinical and radiographic outcomes for lumbosacral fusion (in patients with spinal deformity) using a combination of bilateral sacral and iliac screws with a minimum 5-year follow-up.

SUMMARY OF BACKGROUND DATA

To our knowledge, long-term results (>5 years of follow-up) of bilateral S1 screw/bilateral iliac screw fixation have never been published or presented.

MATERIALS AND METHODS

A total of 67 patients (from an initial consecutive cohort of 81) undergoing lumbosacral fusion with bilateral sacral and iliac screws with a minimum follow-up of 5 years (range 5-10 + 5, average 6 + 3) were analyzed for radiographic outcome and clinical course by an outcome questionnaire (administered at ultimate follow-up) analysis. Patients were divided into 2 groups: group 1, 34 patients with mostly high-grade spondylolisthesis; and group 2, 33 with adult scoliosis fused mostly from the thoracic spine to the sacrum. A true anteroposterior pelvis film was obtained in all patients to assess for sacroiliac joint arthritis, as were standard spine radiographs. Patients were administered Oswestry and directed buttock pain questionnaires at latest follow-up.

RESULTS

There were no cases of sacral screw failure (i.e., screw loosening, partial screw pullout, or fracture of the sacral screw). There were 5 cases of nonunion at L5-S1. Of the 5 cases, 3 did not have anterior column support at L5-S1. Four of the 5 cases were revised, and, subsequently, 3 achieved union. Iliac screws were removed electively on 1 or both sides in 23 of the patients after 2 years postoperatively because of prominence. There were 7 cases of iliac screw breakage. Iliac screw halos were observed in 29 patients. No sacroiliac osteoarthritis was observed on the true anteroposterior pelvis films. At ultimate follow-up, average visual analog painscale (0-10) score to assess buttock pain was 2.4, and average Oswestry score was 20.1.

CONCLUSIONS

For high-grade spondylolisthesis and long adult deformity fusions to the sacrum, a montage of bilateral S1 screws and iliac screws were effective in protecting the sacral screws from failure. Pseudarthrosis at L5-S1 was manifested by rod breakage at that level. We saw no evidence of a long-term effect of the iliac screws predisposing the sacroiliac joints to degeneration at follow-up ranging from 5 to 10 years.

Utilization of iliac screws and structural interbody grafting for revision spondylolisthesis surgery

STUDY DESIGN

Retrospective case analysis and presentation.

OBJECTIVES

The purpose of this article is to discuss the spectrum of failed spondylolisthesis cases for which either anterior column support or iliac screw fixation or both are useful in salvaging failed spondylolisthesis surgeries.

SUMMARY OF BACKGROUND DATA

Past studies and experience have suggested that there is a relatively high rate of sacral screw failure both in long constructs to the sacrum in the adult population and also with treatment of both high-grade and adult spondylolisthesis at L5-S1. It has been noted that anterior column support at L5-S1 and additional fixation points in the sacropelvic unit provide some protection to the sacral screws.

METHODS

This article details the author's personal and institutional experience with sacropelvic fixation and anterior column support at L5-S1 to salvage failed spondylolisthesis cases.

RESULTS

To some extent, each case needs to be individualized. It is not always necessary to provide both anterior column support at L5-S1 and protection of the sacral screws with iliac screws. However, in the most complex problems using both seems to provide the greatest chance for an acceptable radiographic and clinical outcome. Most biomechanical studies have supported the use of anterior column support and iliac fixation to protect sacral screws, suggesting, of the two, that the iliac screws are more valuable.

CONCLUSIONS

For many of these cases of both high-grade dysplastic spondylolisthesis and low-grade adult isthmic spondylolisthesis, a reasonable combination of anterior column support and/or iliac screw fixation may be logical to reduce the incidence of failure and need for revision. The biggest concern with using iliac screw fixation is that these screws are prominent in a percentage of patients and the ultimate impact on the sacroiliac joint is not fully investigated. However, at our institution with 5- to 10-year follow-up, the impact on the sacroiliac joint has been minimal.

The indications for interbody fusion cages in the treatment of spondylolisthesis: analysis of 120 cases

STUDY DESIGN

This study retrospectively examines outcomes of unilateral transforaminal lumbar interbody fusion (TLIF) with posterior fixation using anterior carbon fiber cages and 360 degrees fusion in spondylolisthesis.

OBJECTIVES

The goals were to examine the outcomes and perioperative complications of using anterior column support in the treatment of various types of spondylolisthesis.

SUMMARY OF BACKGROUND DATA

In 2000, Brantigan et al reported the Brantigan interbody fusion cage used as a posterior lumbar interbody fusion in the US IDE clinical trial. This is the largest series to date of TLIF cages specifically used in the treatment of spondylolisthesis.

METHODS

A comprehensive long-term follow-up study was conducted to evaluate the fusion success and morbidity following implantation with an anterior column support and posterior pedicle screw fixation. The 120 patients with spondylolisthesis were comprised by 11 cases, dysplastic; 58 cases, degenerative; and 51 cases, isthmic-acquired spondylolisthesis. Anterior column support was either a rectangular carbon fiber/PEEK device or a cylindrical carbon fiber/PEEK device. Twenty-eight cases (23%) were revisions.

RESULTS

There were no pseudarthrosis, instrumentation failures, or significant subsidence at the TLIF level. The disc space height and foraminal height were restored as part of the surgical procedure. Disc height, as measured from the posterior edge of the superior vertebral body, increased from a mean of 5.6 mm before surgery to a mean of 9.3 mm after surgery. Although reduction of the slip was not the primary goal during the surgical procedure for the 120 cases with spondylolisthesis (isthmic-acquired = 51, degenerative = 58, and dysplastic = 11), the 23% slip reduction achieved at surgery was maintained at follow-up. Mean operative time was 143 +/- 33 minutes (range, 70-255 minutes) for all cases. Mean blood loss was 724 +/- 431 mL (range, 300-2,500 mL). There were seven incidental durotomies and three infections. One patient with Grade I degenerative spondylolisthesis required revision of the carbon fiber cage for posterior migration secondary to a traumatic event 3 months after surgery. Fusion success was 98% using the criteriaof Lenke for the posterior fusion and Brantigan and Steffee for the TLIF graft incorporation.

CONCLUSIONS

Interbody cages in spondylolisthesis are useful to increase neuroforaminal height, to facilitate reduction, and to improve the chances of achieving a successful 360 degrees fusion.

High-grade isthmic dysplastic spondylolisthesis: monosegmental surgical treatment

STUDY DESIGN

A prospective single arm cohort. OBJECTIVE.: To study the results of distraction reduction of high-grade isthmic dysplastic spondylolisthesis with posterior lumbar interbody fusion and posterior compression in a consecutive, prospectively collected series of adolescent patients.

SUMMARY OF BACKGROUND DATA

High-grade isthmic dysplastic spondylolisthesis has been associated with a high complication and failure rate regardless of the method of surgical treatment, including in situ fusion, cast correction and fusion, anterior fusion, posterior instrumented fusion, and combination procedures.

METHODS

A total of 18 adolescents with the diagnosis and a minimum 50% slip underwent the procedure of Gill decompression, temporary distraction with reduction of the deformity, complete lumbosacral discectomy, posterior lumbar interbody fusion with Harm's cage and autogenous iliac graft, and posterior monosegmental compression instrumentation with pedicular fixation.

RESULTS

Follow-up ranged from 2.3 to 5 years. Slip improved from 77% to 13% and slip angle from 35 degrees to 3.8 degrees initially and 4.3 degrees at final follow-up. One patient had loss of 16 degrees of slip angle but achieved arthrodesis. Sacral inclination improved from 28 degrees to 39 degrees . There were no neurologic or infectious complications. There were no overt instrumentation failures. Arthrodesis was achieved in every instance. Two patients had structural complications, neither of which underwent reoperation.

CONCLUSIONS

The index procedure provided near-anatomic correction of high-grade spondylolisthesis, which is maintained at a minimum 2-year follow-up without significant complications. There were two structural complications. Anterior column structural support and posterior compressive instrumentation help restore the necessary biomechanics to allow clinical fusion and success. This series has led the senior author to evolve his technique too ften include caudad fixation to the pelvis and/or cephalad fixation to L4.

Tratamento da instabilidade lombar com parafusos pediculares

A instabilidade lombar é uma doença freqüente na prática clínica. Vários autores preconizam o uso de parafusos pediculares para fixação da artrodese posterior, demonstrando melhores resultados do que a estabilização in situ. OBJETIVO: Avaliar o resultado funcional e radiográfico dos pacientes que procuraram o Grupo de Coluna da Faculdade de Ciências Médicas da Santa Casa de São Paulo portadores de instabilidade lombar submetidos ao tratamento cirúrgico pela artrodese vertebral por via posterior utilizando-se fixação metálica representada por parafusos pediculares. MÉTODOS: Foram coletados dados dos prontuários médicos do Serviço de Arquivos Médicos (S.A.M.E) da Irmandade da Santa Casa de Misericórdia de São Paulo e avaliação por meio de radiografias simples nas incidências frente, perfil e oblíquas para estudos de imagem além da avaliação funcional pré e pós-operatória, com seguimento mínimo de dois anos. RESULTADOS: Durante o período de Novembro de 1995 à Junho de 2000 avaliamos dez pacientes portadores de instabilidade lombar degenerativa (48%), cinco pacientes com espondilolistese ístmica (23%) e seis com estenose lombar degenerativa (29%). Quanto à avaliação funcional, obtivemos 76% de resultados excelentes e bons. As complicações verificadas foram infecção superficial, pseudartrose e posicionamento inadequado dos parafusos (19%). CONCLUSÕES: Os autores concluem que este método de fixação é eficaz, apresentando fusão da artrodese em 95% dos pacientes.

Long adult deformity fusions to L5 and the sacrum. A matched cohort analysis

STUDY DESIGN

A matched cohort analysis of long adult deformity fusions according to distal fusion level (L5 vs. S1). OBJECTIVE.: To compare the results of long adult deformity fusions to either L5 or the sacrum in the presence of a "healthy" 5-1 disc using a matched cohort analysis.

SUMMARY OF BACKGROUND DATA

For adult spinal deformity, the decision often arises whether to terminate a long fusion at L5 or the sacrum. The decision is especially challenging in the presence of a "healthy" (Grade 0 to 1 degeneration) 5-1 disc.

MATERIALS AND METHODS

A total of 95 adult deformity patients that underwent fusion from the thoracic spine to either L5 or the sacrum were sorted according to five preoperative criteria: 5-1 disc status, patient age, smoking status, number of levels fused, and sagittal balance. Two cohorts (L5, 27 patients; sacrum, 12 patients) were precisely matched according to the five criteria. Patients were evaluated at 2-year minimum follow-up according to radiographic data, complications, and SRS-24 outcomes.

RESULTS

Correction of sagittal imbalance was superior for sacrum patients (C7 plumb line: L5, 0.9 cm; sacrum, 3.2 cm; P = 0.03). At latest follow-up (L5, 5.2 years; sacrum, 3.7 years), 67% of L5 patients had radiographic evidence of advanced 5-1 disc degeneration and the L5 cohort tended to have inferior sagittal balance (C7 plumb line: L5, +4.0 cm; sacrum, +1.2 cm; P = 0.06). The sacrum cohort, however, required more surgical procedures (L5, 1.7; sacrum, 2.8; P = 0.03) and experienced a greater frequency of major complications (L5, 22%; sacrum, 75%; P = 0.02), including nonunion (L5, 4%; sacrum, 42%; P = 0.006) and medical morbidity (L5, 0%; sacrum, 33%; P = 0.001). SRS-24 scores reflected a similar patient assessment of outcome and function for the two cohorts (L5, 89; sacrum, 87).

DISCUSSION AND CONCLUSION

At 3 to 5 years' mean follow-up, long adult fusions to the sacrum required more procedures and had a higher frequency of complications than similar fusions to L5. For fusions to L5, subsequent subjacent disc degeneration is common and may be associated with a forward shift in sagittal balance. The ultimate influence of these factors on long-term outcomes remains to be seen.