Iliac screw fixation in neuromuscular scoliosis

The Influence of Radiographic Parameter on the S2 Alar-Iliac Screw Virtual Trajectory in Degenerative Lumbar Scoliosis Patients: A Computed Tomography Study

OBJECTIVE

S2 alar-iliac (S2AI) screw had been widely used in the pelvic fusion for degenerative lumbar scoliosis (DLS) patients. However, whether S2AI screw trajectory was influenced by sagittal profile in DLS patients had not been comprehensively investigated. The objective of this study was to evaluate the associations between the optimal S2 alar-iliac (S2AI) screw trajectory and sagittal spinopelvic parameters in DLS patients.

METHODS

Computed tomography (CT) scans of pelvis were performed in 47 DLS patients for three-dimensional reconstruction of S2AI screw trajectory from September 2019 to November 2021. Five S2AI screw trajectory parameters were measured in CT reconstruction images, including: 1) angle in the transverse plane (Tsv angle); 2) angle in the sagittal plane (Sag angle); 3) maximal screw length; 4) screw width; and 5) skin distance. The lumbar Cobb angle, lumbar apical vertebral translation (AVT); global kyphosis (GK); thoracic kyphosis (TK); lumbar lordosis (LL); sagittal vertical axis (SVA); sacral slope (SS); pelvic tilt (PT); and pelvic incidence (PI) were measured in standing X-ray films of the whole spine and pelvis.

RESULTS

Both Tsv angle and Sag angle had significant positive associations with SS (p < 0.05) but negative associations with both PT (p < 0.05) and LL (p < 0.05) in all cases. Patients with SS less than 15° had both smaller Tsv angle and Sag angle than those with SS equal to or more than 15° (p < 0.05). The decreased LL would lead to the backward rotation of the pelvis, resulting in a more cephalic and less divergent trajectory of S2AI screw in DLS patients.

CONCLUSIONS

For DLS patients with lumbar kyphosis, spine surgeons should avoid both excessive Tsv and Sag angles for S2AI screw insertion, especially when using free-hand technique.

S2 Alar Screw Insertion Accuracy and Factors Associated With Screw Loosening and Lumbosacral Nonunion

OBJECTIVE

To investigate S2 alar screw (S2AS) accuracy and factors associated with S2AS loosening and lumbosacral nonunion.

METHODS

We retrospectively reviewed patients who underwent lumbosacral fusion surgery with S2AS addition under fluoroscopy. S2AS loosening and lumbosacral nonunion were analyzed using a 1-year postoperative computed tomography. S2AS insertion accuracy was originally classified as accurate, short, anterior perforation, lateral perforation, and sacroiliac joint (SIJ) deviation among lateral perforation. Clinical data including sex, age, body mass index, fused segments, fusion procedure, primary or revision surgery, Japanese Orthopedic Association scores and complications were collected. Factors associated with S2AS loosening and lumbosacral nonunion were analyzed.

RESULTS

A total of 37 patients (74 screws, age: 63.78 ± 13.57 years, female/male: 14/23 patients, body mass index: 23.11 ± 2.53, fused segments: 1-4 levels, revision: 38%) were included. S2AS loosening and lumbosacral nonunion were observed in 18 screws (13%) and 8 patients (22%) respectively. Only 35 screws (47%) were inserted accurately in our classification. Short, lateral perforation, and anterior perforation were observed in 14 screws (19%), 22 screws (30%), and 3 screws (4.1%). SIJ deviation was seen in 15 screws (20%) Factors associated with S2AS loosening were older age (P = 0.038), fusion levels (P = 0.011), and SIJ deviation (P < 0.001). S2AS loosening affects S1 pedicle screw (S1PS) loosening (P = 0.001). Furthermore, S2AS loosening is a risk factor for lumbosacral nonunion (P = 0.046).

CONCLUSIONS

S2AS insertion under fluoroscopy is inaccurate. S2AS loosening induces S1PS loosening and lumbosacral nonunion. Surgeons should avoid deviating to SIJ, especially in older patients and relatively longer fusion.

The indication of fusion to the pelvis in neuromuscular scoliosis is based on the underlying disease rather than on pelvic obliquity

INTRODUCTION

The decision to instrument to L5 or ilium, in NMS, is usually based on radiologic factors, including pelvic obliquity (PO) > 15°, apex of curvature < L3, and Cobb angle > 60°. Since scoliosis in these patients is caused by a neurologic disease, we based our decision to stop at L5 on the presence of spasticity or flaccidity.

PATIENTS & METHODS

The senior author did 109 primary fusions in NMS. Of those with DMD or SMA only 16% were instrumented to the ilium. The main factor for our decision was the correction potential of the truncal shift and PO in the supine traction radiographs and the absence of severe spasticity.

RESULTS

The 57 patients with DMD/SMA had a mean preoperative curvature of 68°, PO of 17°, and truncal shift of 20°. 74% should have been instrumented to the pelvis, but only 16% were. Those instrumented shorter as the rule, were corrected from 74° to 26° and had a postoperative PO of 8°. There was no significant difference in postoperative correction and PO compared to those instrumented to L5 on standard protocol. Subsequent extension to the pelvis was needed in 1 CP patient. There were no significant changes after 2 years. Of the 20 patients instrumented to the pelvis 11 had cerebral palsy and a preop curvature of 89°, a PO of 21° and a truncal shift of 25°.

DISCUSSION

The decision on instrumentation length should take flexibility and disease into consideration. If the trunk is centred over the pelvis, deterioration will not occur in absence of spasticity.

Digital anatomical study and clinical application of the ideal S2 alar-lliac screw trajectory

BACKGROUND

To investigate the ideal trajectory for the S2AI screw and to clinically validate its safety feasibility.

METHODS

The 3D model was reconstructed from CT data of the pelvis of 30 selected adults, and the 3D coordinate system was established with the first sacral superior endplate as the horizontal plane. A set of cutting planes was made at 3 mm intervals in the coronal plane, and the cross-sectional internal tangent circles were divided in the target area. Using the linear fitting function, the axis of 90 mm length was calculated by the least squares method for each inner tangent circle center. The diameter of the axis is gradually increased until the first contact with the cortex, and the cylindrical model is the ideal screw trajectory. The intersection of the axis and the dorsal cortex is the screw placement point, which is located by Horizon Distance (HD) and Vertical Distance (VD); the diameter of the screw trajectory (d) is the diameter of the cylindrical model; the direction of the screw trajectory is determined by Sagittal Angle (SA) and Transverse Angle (TA). The screw trajectory orientation is determined by Sagittal Angle (SA) and Transverse Angle (TA). Based on the ideal screw trajectory, the 3D printed surgical guide and freehand techniques were used to verify its safety feasibility, respectively.

RESULTS

The screw placement points [HD (4.7 ± 1.0) mm, VD (19.7 ± 1.9) mm], screw placement directions [SA (31.3°±2.3°), TA (42.4°±2.3°)], and screw dimensions for the ideal screw trajectory of the S2AI were combined for analysis. (L is 90 mm, d is 13.2 ± 1.4 mm). The S2AI screw superiority rate [96.6% (56/58)] and reasonable rate [100%] were higher in the guide group than in the freehand group [90.0% (63/70), 97.1% (68/70)], but the differences were not statistically significant (P > 0.05). Although screws invaded the cortex in both groups, there were no associated adverse events in either group.

CONCLUSION

The S2AI screw-based ideal trajectory placement is a safe, feasible and accurate method of screw placement.

RADIOGRAPHIC EVALUATION OF SURGICAL CORRECTION OF SCOLIOSIS DUE TO CEREBRAL PALSY USING INTRA-OPERATIVE TRACTION AND NEW CORRECTION TECHNIQUE WITH 3RD PROVISIONAL ROD

ABSTRACT Objective: Evaluate the radiographic results of patients with cerebral palsy and Lonstein and Akbarnia type II scoliosis who underwent intraoperative halofemoral traction (IFAT) and correction with a 3rd provisional nail. Methods: Retrospective case series study. Were evaluated preoperative (PRE), traction (TR), immediate (POI), and late (POT) total spine radiographs. Were verified the angular value of the main curve (COBB), pelvic obliquity (OP), trunk balance in the coronal plane (CSVA), vertical sagittal alignment (SVA), curve flexibility, and percentage of correction in the final PO. Friedam and Wilcoxon tests were performed (p<0.05). Results: Twenty-one patients were included in the study, with a mean age of 16 (±4.13). There was a statistical difference when comparing COBB PRE with TRACTION to POI and POT (p=0.0001), OP in PRE with TRACTION, and between PRE and POT (p=0.0001). There was a statistical difference in coronal (CSVA) and sagittal (SVA) balance concerning PRE and POT. The percentage of correction for the main curve was 55.75% (± 11.11), and for the O P, 64.86% (± 18.04). Conclusion: The correction technique using the 3rd provisional nail technique and intraoperative traction presents a correction power of 55.75% of the proximal curve and 64% of the pelvic obliquity. In addition, it is easy to assemble, has a short surgical time, and causes little loss of correction during follow-up. Level of Evidence III B; I study a series of retrospective cases.

When Should Instrumentation to the Pelvis be Considered in Minimally Ambulatory Adolescents With Neuromuscular Scoliosis?

INTRODUCTION

The goal of neuromuscular scoliosis (NMS) surgery is to improve sitting balance, facilitate daily care, and alleviate pain. In nonambulatory patients, where sitting balance is key, fusion to the pelvis is usually required. However, in minimally ambulatory patients, fusion to the pelvis remains controversial, and there is considerable practice variability in this patient population. The purpose of this study is to evaluate and summarize the available evidence regarding fusion constructs in minimally ambulatory patients with NMS and to provide expert opinion regarding when fusion to the pelvis should be considered.

METHODS

A search of the English literature was performed using PubMed to identify papers pertaining to patients with NMS treated with instrumented posterior spinal fusion. Papers published before 2000, case reports, and level V evidence were excluded.

RESULTS

The authors identified 8 studies for review. The majority included both nonambulatory and minimally ambulatory patients. Structured review of the literature demonstrated fusion to the pelvis may allow for greater curve and pelvic obliquity correction, but it is also associated with increased blood loss and operative time. There is no evidence that fusing to the pelvis decreases ambulatory status in minimally ambulatory patients.

CONCLUSIONS

In minimally ambulatory patients with NMS, fusion short of the pelvis may be considered in patients with adequate head control without the presence of hip subluxation or dislocation and when pelvic obliquity is <15 degrees. Fusion to the pelvis is recommended in patients who do not meet these criteria.

Utilization of Offset Iliac Connectors as Anchoring Sites in Severe Rigid Scoliosis: New Technique

STUDY DESIGN

This was a prospective cohort study.

OBJECTIVES

To introduce the iliac connectors as fixation options in spinal constructs used for correction of severe scoliosis at locations other than the lumbopelvic region.

METHODS

Nine patients with severe rigid scoliosis undergoing surgical release and posterior instrumentation in the period between January 2013 and January 2015 were included in this prospective cohort study. Mean age was 18.4 years; 8 had triple structural curves, and the remaining patient had double structural curves. Cobb angles of the primary and compensatory curves were compared with the immediate, 1-year, and 2-year postoperative measurements using the F test, with P value ≤.05 indicating statistical significance. Screw densities of the final constructs were calculated and compared with the screw densities when the offset iliac connectors were not used.

RESULTS

One to 4 offset iliac connectors were used in all 9 patients, increasing screw density by a mean of 6.24 (P < .001). The mean Cobb angle of the major curve was corrected from 98.44° to 58.2° (P < .001), that of the first compensatory curve, from 56.55° to 38.33° (P < .001), and that of the second compensatory curve, from 40.75° to 26.63° (P < .001). There were no intraoperative neurological complications. After a mean follow-up of 30.6 months, the construct remained stable in all patients with no loss of correction.

CONCLUSION

Offset iliac connectors can be a valuable tool to increase screw density in correction of severe scoliosis, thus increasing overall biomechanical strength of the final construct.

Surgical treatment of scoliosis in Ullrich Congenital Muscular Dystrophy: a case series of 3 patients

Scoliosis in Ullrich Congenital Muscular Dystrophy (UCMD) is very common, with a reported incidence of more than 50%, and it is rapidly progressive. There are no previous studies which specifically focus on scoliosis surgery in UCMD patients. This article reports three cases of scoliosis surgery in UCMD, focusing on operative course, clinical and radiological results achieved, fusion area and complications, with a 2-year follow-up. The surgical technique adopted for vertebral arthrodesis included: high-density pedicle screw systems, asymmetric rods contouring and direct vertebral rotation. The summary results shown a significative correction of the coronal deformity, with a reduction of the mean Cobb angle from 49° to 25° post-operatively. Mean pelvic tilt remained stable, while L5-tilt showed a decrease from 10° to 6°. Mean screw density was 1.92. None of the patients required extended fixation to S2. No major complications were reported, and patients maintained their pre-operative walking ability. All the patients reported a subjective improvement in quality of life, with a better sitting comfort. In conclusion, posterior spinal fusion with high-density pedicle screw systems and direct vertebral rotation may be safe and effective in surgical correction of scoliosis in UCMD. If pelvic obliquity and L5-tilt are less than 15°, could be possible to achieve an optimal spinal and pelvic balance even without sacral or pelvic fixation.

Clinical Effectiveness of S2-Alar Iliac Screws in Spinopelvic Fixation in Pediatric Neuromuscular Scoliosis: Systematic Literature Review

STUDY DESIGN

Systematic literature review.

OBJECTIVES

To comprehensively review the S2-alar iliac (S2-AI) screw technique for pelvic fixation in pediatric neuromuscular scoliosis.

METHODS

Articles identified from the PubMed and EMBASE databases were reviewed for relevance and applicability, and the studies were summarized.

RESULTS

Eight articles met the inclusion criteria. A total of 277 pediatric patients underwent spinopelvic fixation using S2-AI fixation for neuromuscular scoliosis; the mean follow-up was 3 years (range = 0.75-6 years). Six articles had level III evidence (5 retrospective cohort studies, 1 observational study), and 2 articles had level IV evidence (case series). Wound complications occurred in 34 (12.2%) patients. Instrumentation complications occurred in 36 patients (13.0%), including lucency around the screw (6.5%), screw fracture (3.6%), disengaging of the set/screw or rod from the tulip head (2.8%), and screw displacement (0.7%). Three patients (1.1%) required reoperation for instrumentation failures. The overall reoperation rate-including 3 hardware replacements and 3 cases of L5-S1 pseudarthrosis-was 2.1%. The mean Cobb angle correction was 51.4°, and the mean pelvic obliquity correction was 14.8°; deformity correction was maintained at 3- and 5-year follow-ups. There were 10 (3.6%) cases of implant prominence/implant-related pain, 1 case of sacroiliac joint pain (resolved with longer screw placement), and no major neurological or vascular complications secondary to S2-AI screw placement.

CONCLUSIONS

This review suggests that the use of S2-AI screws in pediatric neuromuscular scoliosis is efficacious with a reasonable safety profile and provides a useful technique for pelvic fixation in children with scoliosis.

Comparison of the 3D-printed operation guide template technique and the free-hand technique for S2-alar-iliac screw placement

BACKGROUND

To compare the safety and accuracy of the 3D-printed operation guide template technique and the free-hand technique in the placement of the S2-alar-iliac (S2AI) screw.

METHODS

We conducted a retrospective analysis of 47 patients undergoing S2AI screw placement in our hospital, divided into the 3D-printed operation guide template group and the free-hand screw placement group. The duration of single S2AI screw placement was documented in all patients. A postoperative CT scan was performed to assess screw placement effectiveness according to the distance from the screw tip to the breach of the cortical bone wall.

RESULTS

In total, 42 screws were placed in the guide template group, with an average screw placement duration of 151.6 ± 44.8 s. Screw placement grading was as follows: 40 screws in grade 0, two in grade 1, and none in grades 2 and 3. This grading resulted in excellent and good rates of 95.2% and 100%, respectively. In total, 52 screws were placed in the free-hand group, with an average screw placement duration of 138.3 ± 45.9 s. Screw placement grading was as follows: 42 screws in grade 0, seven in grade 1, three in grade 2, and none in grade 3. This grading resulted in excellent, good and acceptable rates 80.8%, 94.2% and 100%, respectively. Screw placement duration did not significantly differ between the groups (p > 0.05). The excellent rate of screw placement was greater in the guide template group than in the free-hand group (p < 0.05), but the good and acceptable rates did not significantly differ between the two groups (p > 0.05).

CONCLUSION

Both techniques can be applied to S2AI screw placement. The 3D-printed guide technique is superior to the free-hand technique in terms of safety and accuracy.

Accuracy of S2 Alar-Iliac Screw Placement Under the Guidance of a 3D-Printed Surgical Guide Template

OBJECTIVE

To evaluate the safety and accuracy of S2 alar-iliac (S2AI) screw placement guided by a 3-dimensional (3D)-printed surgical guide template.

METHODS

The data of 27 patients treated with S2AI screws were analyzed. S2AI surgical guide templates were designed and printed, and S2AI screw placement was completed intraoperatively with the guide templates. Postoperative computed tomography was performed to measure screw path parameters, namely the sagittal angle (SA), the transverse angle (TA), the horizontal distance (HD) between the entry point of the screw and the median sacral crest, and the vertical distance (VD) between the entry point of the screw and the lower edge of the first posterior sacral foramen. Screw placement was graded according to the Oh grading criteria.

RESULTS

A total of 54 S2AI screws were placed. The screw grades were as follows: 52 screws were considered grade 0, 2 were grade 1, none were grade 2, and none were grade 3. Thus grade 0 accounted for 96.3% of the screws. When the preoperatively planned SA (32.3° ± 2.0°), TA (42.1° ± 3.9°), HD (5.1 ± 1.1) mm, and VD (19.0 ± 2.4) mm were compared with the corresponding postoperative SA (31.9° ± 3.8°), TA (42.5° ± 4.0°), HD (4.9 ± 1.1) mm, and VD (19.1 ± 2.3) mm, no significant differences were identified (P > 0.05).

CONCLUSIONS

S2AI screw placement assisted by a 3D-printed surgical guide is safe and accurate.

The Value of a Modified Wiltse Approach for Deformity Correction in Neuromuscular Scoliosis

Background

Wiltse approaches have been shown to reduce operative blood loss and enhance recovery in lumbar spinal surgery; however, their efficacy in neuromuscular scoliosis (NMS) deformity correction has never been assessed. Thus, the purpose of this study was to compare the outcomes of deformity correction requiring pelvic fixation in NMS performed through a Wiltse approach in contrast to a standard midline approach.

Methods

This is a retrospective review of 24 consecutive children with NMS undergoing deformity correction by a single surgeon in our institution. Patient demographic data, operative time, blood loss, curve correction, length of stay, and complications were recorded.

Results

In 16 children, the procedure was performed through a Wiltse approach and in 8 through a midline approach. There was no significant difference in age, sex, preoperative Cobb angle, or number of levels fused. Patients who underwent a Wiltse approach had significantly less blood loss yet similar curve correction. The hospital length of stay and complication rate were not significantly different between the groups.

Conclusions

A modified Wiltse approach can be safely used for NMS deformity correction. This approach achieves similar curve corrections to a traditional midline approach with less blood loss and no need for iliac screw connectors.

Level of Evidence

3.

Spine deformities in patients with cerebral palsy; the role of the pelvis

INTRODUCTION

Progressive neuromuscular spinal deformities with pelvic obliquity and loss of sitting balance are typical features of severely affected patients with cerebral palsy. The pelvis represents the key bone between the spine and the lower extremity when it comes to deciding whether and when to operate and if spine or hip surgery first is beneficial. The pelvis can be looked at as the lowest vertebra and as the rooftop of the lower extremities.

BIOMECHANICAL CONSIDERATIONS

To allow for a normal spinal shape, the pelvis needs to be horizontal in the frontal plane and mildly anterior tilted in the sagittal plane, less for sitting and more for standing. Any abnormal pelvic position requires spinal compensation and challenges the equilibrium control of the individual. Both anatomical neighbourhoods - the spine and the hip joints - have to be considered when spinal deformities, hip instability and contractures evolve, in conservative therapy (bracing, physiotherapy, seating in the wheelchair) and when surgical interventions are weighed out against each other.

SURGICAL CONSIDERATIONS

Multiple anatomical factors such as sagittal profile and pelvic orientiation, pelvic transverse plane asymmetries and lumbosacral malformations have to be considered in case the pelvis is instrumented with sacral and iliac screws. Rotational deformities and asymmetries of the pelvic bones make the safe insertion of long screws challenging. Advantages of primary pelvic fixation include correction of pelvic obliquity, especially considering the lever arm of the whole spinal construct. The risk of revision surgery due to progression of distal curves is also reduced. Disadvantages of pelvic fixation include the complexity of the additional intervention, which may result in longer operating times, increased risk of blood loss, infection and hardware malpositioning.

Morphometric measurement and applicable feature analysis of sacral alar-iliac screw fixation using forward engineering

PURPOSE

To evaluate S1AI-S4AI screw channels with three-dimensional digital technology simulation analysis and to study the feasibility and applicable features of sacral alar-iliac screw fixation in adults.

MATERIALS AND METHODS

Forty (20 men and 20 women) normal adult's pelvic CT scan data sets were selected to reconstruct the three-dimensional pelvic model. The ideal S1AI-S4AI screw channels were simulated, followed by precise measurement of their parameters.

RESULTS

The results showed that there were no significant differences in the transverse angles, sagittal angles, radiuses of the maximal inscribed circles, or lengths of the screw channels in S1AI-S2AI screws between genders (P > 0.05). In contrast, the radiuses of the maximal inscribed circles on the left and right, respectively, were 5.93 ± 1.02 mm and 5.92 ± 1.04 mm in males and 4.64 ± 0.98 mm and 4.59 ± 0.95 mm in females, and there was a significant difference in S3AI screws between genders (P < 0.05). With a radius of 2.50 mm considered to be standard, there were 25 cases (62.5%) with an S4AI screw channel radius ≤ 2.50 mm in 40 adults, and 15 cases (37.5%; 9 males and 6 females) with a radius > 2.50 mm. Furthermore, the transverse angles, the sagittal angles, the lengths of the screw channels, and the radiuses of the maximal inscribed circles were significantly different between genders in 15 cases (P < 0.05).

CONCLUSION

Only one maximum ideal screw can be placed on one side at a time. With a radius of 2.50 mm considered to be standard, it is feasible to place S1AI-S3AI screws with a radius > 2.50 mm in the entire adult population and S4AI screws with a radius > 2.50 mm in some of the adult population. Furthermore, preoperative three-dimensional reconstruction and three-matic research software can effectively simulate the sacral alar-iliac screw channels, and they can provide accurate data for clinical applications.

Pelvic Obliquity Correction in Distraction-Based Growth Friendly Implants

DESIGN

Multicenter retrospective review.

OBJECTIVE

To evaluate radiographic outcomes and complication rates of patients treated with distraction based implants and pelvic fixation with either screws (sacral-alar-iliac [SAI] screws or iliac screws) or hooks (S hook iliac fixation).

SUMMARY OF BACKGROUND DATA

Multiple options exist for pelvic fixation in distraction-based growing rod systems; however, limited comparative data are available.

METHODS

Early-onset scoliosis (EOS) patients of all diagnoses with distraction-based implants that had pelvic fixation from 2000 to 2013 were reviewed from two EOS multicenter databases. Patients were divided into two groups by type of pelvic fixation: (1) screw group (SAI screws or iliac screws) or (2) S hooks. Exclusion criteria were as follows: index instrumentation ≥10 years old and follow up <2 years. A total of 153 patients met the inclusion criteria. Mean age at index surgery was 6.1 years (range 1.0-9.9 years) and mean follow-up was 4.9 years.

RESULTS

Pelvic fixation in the 153 patients was as follows: screw group = 42 and S hook group = 111. When comparing patients with >20° of initial pelvic obliquity, the screw group had significantly more correction; mean 26° ± 13° for the screw group versus mean 17° ± 7° in the S hook group (p = .039). There was no significant difference in change in T1-S1 length (40 vs. 39 mm, p = .89) or correction of Cobb angle (30° vs. 24°, p = .24). The total complication rate for the screw group was 14% (6/42) versus 25% (28/111) in the S hook group, though this did not achieve significance (p = .25). The most common complications were device migration (13), implant failure (8), and implant prominence (4) for S hooks and implant failure (3), implant prominence (2), and device migration (1) for the screw group.

CONCLUSION

In distraction-based growth-friendly constructs, pelvic fixation with screws achieved better correction of pelvic obliquity than S hooks. Complications were almost twice as common with S hooks than screws, though this did not reach statistical significance.

Don't You Wish You Had Fused to the Pelvis the First Time: A Comparison of Reoperation Rate and Correction of Pelvic Obliquity

STUDY DESIGN

A multicenter retrospective study.

OBJECTIVE

The aim of this study was to compare pelvic obliquity correction and reoperation rate in neuromuscular scoliosis patients who had their pelvis included in a posterior spinal fusion (pelvic fusion, PF) at their index procedure versus revision procedures.

SUMMARY OF BACKGROUND DATA

There is limited information on outcomes specific to fusing to the pelvis for neuromuscular scoliosis in a revision operation versus index surgery.

METHODS

Charts and radiographs were reviewed of patients with PF for neuromuscular scoliosis from January 2003 to August 2015 at four high-volume pediatric spine centers with >2 year follow-up.

RESULTS

Two hundred eighty-five patients met inclusion criteria; 271 had PF done at index surgery and 14 had PF done during revision surgery. Before index procedure, there were no significant differences in Cobb angle (P = 0.13). Before PF, there was no difference in pelvic obliquity (P = 0.26). At the time of fusion to the pelvis, estimated blood loss (P = 0.23) and operative time (P = 0.43) did not differ between index and revision groups. Percent correction in pelvic obliquity was similar for both groups (P = 0.72). Overall, 69 patients had complications requiring return to the operating room. Excluding the revision surgery for inclusion of the pelvis for the revision group, there was still a lower reoperation rate with index PF (22.9%, n = 62/271) than revision PF (50.0%, n = 7/14) (P = 0.02). Implant failures were significantly higher in the revision group (index = 7.4%, 20/271; revision = 42.9%, 6/14; P < 0.001).

CONCLUSION

PF at the index spinal fusion led to similar correction of pelvic obliquity with approximately half the reoperation rate compared with PF at a revision surgery. Operative time and blood loss were similar between index and revision spinal fusion.

LEVEL OF EVIDENCE

4.

Second Sacral Alar Screw Fixation: Anatomic Study of Three-Dimensional Computed Tomography and Case Report

OBJECTIVE

S2 alar screw would be an alternative choice without breaking the sacroiliac joint. The aim of this study was to measure radiographic parameters for optimal placement of posterior S2 alar screw for instrumentation and fusion.

METHODS

Three-dimensional computed tomography scans of the pelvis of 60 normal adults were used to map the S2 alar screw. Entry point was typically chosen lateral and superior to the S2 dorsal foramen. Ideal S2 alar screw trajectories were explored by rotating the three-dimensional pelvis, while ensuring trajectories were of maximum length and width. After identification of an optimal trajectory, related linear anatomic parameters and sagittal and transverse angles were determined.

RESULTS

Ideal S2 alar screw trajectories were identified in each computed tomography scan. According to this morphometric study, trajectories for female patients were more lateral in the transverse plane (female 33.73 ± 5.99° vs. male 29.82 ± 4.11°, P < 0.001). Maximal length of trajectory in male patients was significantly longer than in female patients (female 40.82 ± 4.29 mm vs. male 43.42 ± 4.02 mm, P = 0.001). Fourteen S2 alar screws were used in 7 patients with high-grade spondylolisthesis, scoliosis, or nonunion at lumbosacral site. No complications occurred during S2 alar screw placement. One S2 screw failed owing to severe local osteoporosis. No patient developed local pain or wound-related problems.

CONCLUSIONS

S2 alar screw is an alternative sacral fixation point to provide additional biomechanical stability of lumbosacral constructs. A trajectory with maximum length through the S2 ala can be determined using three-dimensional computed tomography.

SACROPELVIC FIXATION USING ILIAC SCREWS: EVALUATION OF TECHNIQUE AND COMPLICATIONS

ABSTRACT Sacropelvic fixation arose from the need to protect the sacral instrumentation in long constructions, due to failures in the implant-bone interface and the treatment of diseases in which there is no possibilities of sacral fixation such as infections and tumors. Due to anatomic difficulties and the complex spinopelvic biomechanics several techniques were developed. The fixation with iliac screws has become according to multiple studies, a well-established technique that minimizes frequent complications such as pseudoarthrosis and implant failure. However, it has disadvantages such as iliac wing fracture and skin lesions due to the protrusion of materials. The present study aims to comprehensively review the literature on the technique taking into account relevant aspects to its better knowledge and application. Level of evidence III; Therapeutic Study.

The comparison of the results after spinal fusion with or without iliac screw insertion in the treatment of neuromuscular scoliosis

Introduction

Neuromuscular scoliosis leads to a wide range of spinal disorders which disturb the musculoskeletal system. The aim of this study is to compare the clinical and radiological results of posterior spinal fusion with and without extending the instrumentation to iliac bones in treatment of neuromuscular scoliosis.

Methods

Medical records and radiographies of 36 patients with neuromuscular scoliosis who underwent posterior instrumentation between 2011 and 2015 were reviewed. Age and body mass index at time of surgery, underlying diagnosis, gender, postoperative infection rates, perioperative and postoperative blood transfusion, duration of surgery, complication rates were identified for each patient retrospectively. SF-36 physical questionnaire was applied to all patients. Surgery was performed in each patient and included posterior spinal fusion with pedicle screws from the proximal thoracic spine (T2 or T3) to S1 (Group A) or extension of distal instrumentation to pelvis by bilateral iliac screws (Group B).

Results

A total of 23 patients in group A were compared with 13 patients in group B. Median age was 14 (9–38) years for group A and 16 (12–25) years for group B. Median follow-up period was 20 (12–66) months. Preoperative median Cobb angles were 66^° and 60^° and postoperative Cobb values were 33^° and 31^° in group A and B respectively. Median Cobb angle reduction was 40^° and 34^° for group A and B. We are able to see in this study that the usage of illiac screws do not increase implant failure and help achieve better functional results.

Conclusion

This study shows that the extention of instrumentation to the pelvis with illiac screws can be beneficial in terms of functional and complicational incidences.

Level of evidence: Level III, therapeutic study.

Sacral Alar Iliac (SAI) Screws Fail 75% Less Frequently Than Iliac Screws in Neuromuscular Scoliosis

BACKGROUND

Despite recent popularity of sacral alar iliac (SAI) screws for fusion to the pelvis for neuromuscular scoliosis, there are little data regarding the failure rate of this technique compared with traditional modes of iliac fixation. Theoretical advantages of the SAI screws are obviating the need for a rod to iliac screw connector and a lower implant profile. The purpose of this study is to determine whether SAI screws have fewer failures than iliac screws in neuromuscular scoliosis.

METHODS

Review of neuromuscular patients treated with posterior spinal fusion with pelvic fixation from 2004 to 2012 with minimum 2-year follow-up was conducted. Medical records and imaging studies were reviewed. Patients were divided into 2 groups based on the type of pelvic fixation (SAI or iliac screws), and implant failures were compared between the groups.

RESULTS

A total of 101 patients were reviewed, including 55 patients with iliac screws and 46 patients with SAI screws. Implant failures included: disengagement of the rod to iliac screw connector (10%, 10/101), separation of screw head from screw shaft (4%, 4/101), and set screw disengagement (2%, 2/101). The SAI group had a lower implant failure rate (7%, 3/46) compared with the iliac screw group (24%, 13/55) (P=0.031). Rod to iliac screw connectors failed in 18% (10/55) of patients. There were significantly less surgical revisions in the SAI group (2%, 1/46) for pelvic screw prominence compared with the iliac screw group (11%, 6/55) (P=0.027).

CONCLUSIONS

SAI screws had a lower rate of implant failure and revision surgery compared with iliac screws. If rod to screw connector failures are excluded, the failure rate of SAI screws of 6.5% (3/46) is similar to that of iliac screws 5.5% (3/55); therefore, the most important advantage of the SAI technique may be obviating the need for a screw to rod connector.

LEVEL OF EVIDENCE

Level III.

Experience in Perioperative Management of Patients Undergoing Posterior Spine Fusion for Neuromuscular Scoliosis

The objective of this investigation was to determine the outcome of spine fusion for neuromuscular (NM) scoliosis, using Unit Rod technique, with emphasis on complications related to preoperative general health. Between 1997 and 2007, 96 consecutive patients with neuromuscular scoliosis operated on with Unit Rod instrumentation were retrospectively reviewed. The inclusion criteria were diagnosis of NM scoliosis due to cerebral palsy (CP) and muscular dystrophy (DMD). Patient's preoperative general health, weight, and nutrition were collected. Different radiographic and clinical parameters were evaluated. There were 66 CP patients (59 nonwalking) and 30 DMD patients (24 nonwalking). Mean age at surgery was 16.5 years and 13.9 years, respectively. All radiographic measurements improved significantly. Wound infection rate was 16.7% (11% of reoperation rate in CP; 10% in DMD; 3 hardware removal cases). No pelvic fracture due to rod irritation was observed. Unit Rod technique provides good radiographic and clinical outcomes even if this surgery is associated with a high complication rate. It is a quick, simple, and reliable technique. Perioperative management strategy should decrease postoperative complications and increases outcome. A standardized preoperative patient evaluation and preparation including respiratory capacity and nutritional, digestive, and musculoskeletal status are mandatory prior to surgery.

Sacral-Alar-Iliac Fixation in Pediatric Deformity: Radiographic Outcomes and Complications

STUDY DESIGN

Retrospective case series.

OBJECTIVES

To assess the radiographic outcomes and complications of sacral-alar-iliac (SAI) fixation in children.

SUMMARY OF BACKGROUND DATA

Pelvic fixation in children undergoing spinal deformity surgery can be challenging because of complex anatomy, compound biomechanical forces at the lumbosacral junction, and poor bone quality.

METHODS

Radiographic and clinical records of 80 consecutive patients aged 18 years or younger who underwent posterior spinal fusion surgery with SAI fixation by one pediatric orthopedic surgeon and who had a minimum 2 years of follow-up (mean follow-up: 3.5 years, range, 2-7 years) were retrospectively reviewed. Changes in coronal curve magnitude and pelvic obliquity were assessed using Student t tests. Significance was set at a p value less than .05 for all analyses.

RESULTS

Pelvic obliquity correction averaged 77%, from 26 ± 13 degrees before surgery to 6 ± 4 degrees at final follow-up (p < .001); 91% of the patients were corrected to a pelvic obliquity of less than 10 degrees. Coronal curve correction averaged 72%, from 78 ± 27 degrees before surgery to 22 ± 15 degrees at final follow-up (p < .001). No patient had vascular or neurologic complications or died perioperatively. Twenty patients (25%) had radiographic evidence of implant-related problems, of which there were nine screw fractures (all in the neck of screws with ≤8-mm outer diameter). Six patients had symptomatic complications associated with SAI fixation (three patients with pseudarthrosis at the lumbosacral junction, all of whom required revision surgery, two patients with implant prominence, and one patient with pain related to implant). Other complications included seven instances of wound dehiscence, three deep wound infections, and one superficial wound infection.

CONCLUSIONS

SAI fixation provided a low-profile alternative to iliac screws for the correction of pelvic obliquity. The largest possible diameter screws are recommended, ideally >8 mm.

LEVEL OF EVIDENCE

Level 4.

Are S1 Screws a Useful Adjunct to Iliac Screws in Long Fusions to the Sacrum in Cerebral Palsy?

STUDY DESIGN

Multicenter prospective database review of patients with cerebral palsy (CP) and spinal deformity.

OBJECTIVE

To determine if the type of distal fixation is associated with improved correction of coronal deformity or pelvic obliquity (PO) at 2 years in long posterior fusions to the sacrum.

SUMMARY OF BACKGROUND DATA

Multiple techniques are utilized for distal fixation in patients with CP. Although there is emerging evidence that the augmentation of iliac screws with S1 screws may be beneficial, this remains controversial.

METHODS

A prospective, multicenter database was used to identify patients with CP who underwent long posterior fusions to the sacrum. Eighty-eight patients were included, 52 with iliac screws (I) and 36 with iliac and S1 screws (IS) for distal fixation. Preoperative, first erect, and 2-year follow-up radiographs and complications were analyzed. Statistical analysis was performed using ANOVA and repeated measures ANOVA with significance set at P < 0.05.

RESULTS

Scoliosis was the primary deformity in greater than 90% of patients in both groups (P=0.84). Preoperative coronal deformity was similar (I = 83°, IS = 87°, P = 0.49), but correction was better with the use of S1 screws on the first erect radiograph and at 2 years (I = 35°, IS = 22°, P = 0.001), reflecting correction of 58% and 74% for iliac and iliac-S1 screws, respectively (P < 0.001). Preoperative PO was similar (I = 29°, IS = 30°, P = 0.71) and was noted to improve more in the iliac-S1 group by 2 years (I = 11°, IS = 5°, P = 0.004), representing correction of 60% and 77% for the iliac and iliac-S1 groups, respectively (P = 0.018). There was no difference in the rate of major (P = 0.27) or minor (P = 0.65) complications in either group.

CONCLUSION

Bilateral S1 and iliac screws are associated with improved spinal deformity and PO correction at 2 years in the CP population. Two points of distal fixation, S1, and ilium should be considered for this population.

LEVEL OF EVIDENCE

3.

Pelvic Fixation in Adult and Pediatric Spine Surgery: Historical Perspective, Indications, and Techniques: AAOS Exhibit Selection

Achieving solid osseous fusion across the lumbosacral junction has historically been, and continues to be, a challenge in spine surgery. Robust pelvic fixation plays an integral role in achieving this goal. The goals of this review are to describe the history of and indications for spinopelvic fixation, examine conventional spinopelvic fixation techniques, and review the newer S2-alar-iliac technique and its outcomes in adult and pediatric patients with spinal deformity. Since the introduction of Harrington rods in the 1960s, spinal instrumentation has evolved substantially. Indications for spinopelvic fixation as a means to achieve lumbosacral arthrodesis include a long arthrodesis (five or more vertebral levels) or use of three-column osteotomies in the lower thoracic or lumbar spine, surgical treatment of high-grade spondylolisthesis, and correction of lumbar deformity and pelvic obliquity. A variety of techniques have been described over the years, including Galveston iliac rods, Jackson intrasacral rods, the Kostuik transiliac bar, iliac screws, and S2-alar-iliac screws. Modern iliac screws and S2-alar-iliac screws are associated with relatively low rates of pseudarthrosis. S2-alar-iliac screws have the advantages of less implant prominence and inline placement with proximal spinal anchors. Collectively, these techniques provide powerful methods for obtaining control of the pelvis in facilitating lumbosacral arthrodesis.

Early pelvic fixation failure in neuromuscular scoliosis

BACKGROUND

To report on early failures of pelvic fixation in posterior spinal fusions for neuromuscular scoliosis.

METHODS

A retrospective review of posterior-only spinal instrumentation and fusion to the pelvis with iliac screws was performed. Forty-one patients with a mean age of 14 years and mean 16 levels fused met the inclusion criteria. Diagnoses include cerebral palsy (22), Duchenne muscular dystrophy (7), other neuromuscular (10), and spina bifida (2). Cox proportional hazards regression modeling was used to compare rates of failure.

RESULTS

The mean preoperative primary Cobb angle was 82 degrees (range, 21 to 144 degrees). The pelvic obliquity correction was 76%. The fixation in the pelvis failed in 12/41 patients (29%). Failures include: screw head disengaged from screw shaft (5), iliac screw disengaged from rod (2), iliac connector disengaged from rod (2), iliac connector disengaged from iliac screw (4), and iliac screw loosened from bone (3). No failures occurred if there were at least 6 screws in L5, S1, and pelvis (0/7 patients). The failure rate with <6 screws in L5, S1, and pelvis was higher at 35% (12/34 patients) (P=0.16). When using traditional iliac screws with connectors to rods, all constructs had <6 screws in L5, S1, and pelvis. Only 1 failure occurred when S2-iliac screws were used, but was without clinical consequence. The mean time from surgery to failure was 18 months (range, 1 to 49 mo).

CONCLUSION

Not placing bilateral pedicle screws at L5 and S1, in addition to 2 iliac screws, was associated with a 35% early failure rate of pelvic fixation.

LEVEL OF EVIDENCE

Level IV.

Surgical correction of scoliosis in patients with severe cerebral palsy

INTRODUCTION

There is a lack of data in the literature on surgical correction of severe neuromuscular scoliosis in patients with serious extent of cerebral palsy. The purpose of this retrospective cohort study was to analyze the radiological and clinical results after posterior-only instrumentation (group P) and combined anterior-posterior instrumentation (group AP) in severe scoliosis in patients with Gross Motor Function Classification System grades IV and V.

MATERIALS AND METHODS

All eligible patients who underwent surgery in one institution between 1997 and 2012 were analyzed, and charts, surgical reports, and radiographs were evaluated with a minimum follow-up period of 2 years.

RESULTS

Fifty-seven patients were included (35 in group P, 22 in group AP), with a median follow-up period of 4.1 years. The preoperative mean Cobb angles were 84° (34 % flexibility) in group P and 109° (27 % flexibility) in group AP. In group P, the Cobb angle was 39° (54 % correction) at discharge and 43° at the final follow-up, while in group AP the figures were 54° (50 % correction) at discharge and 56° at the final follow-up. Major complications occurred in 23 vs. 46 % of the patients, respectively. Preoperative curve flexibility was an important predictor for relative curve correction, independently of the type of surgery.

CONCLUSION

Posterior-only surgery appears to lead to comparable radiological results, with shorter operating times and shorter intensive-care unit and hospital stays than combined surgery. The duration of surgery was a relevant predictor for complications.

Biomechanical analysis of iliac screw fixation in spinal deformity instrumentation

BACKGROUND

High rates of iliac screw fixation failures have been reported in spinopelvic instrumentations. The objective was to assess the iliac screw loads as functions of instrumentation variables.

METHODS

Spinopelvic instrumentations of six neuromuscular scoliosis were simulated using patient-specific modeling techniques to evaluate the intra- and postoperative iliac screw loads as functions of instrumentation variables: the combined use of sacral screws, the uses of lateral offset connectors and cross-rod connectors, and the iliac screw insertion point and trajectory.

FINDINGS

Sacral screws, lateral connectors and the iliac screw insertion point had significant effects on iliac screw axial forces (69-297N) and toggle moments (0.8-2.9Nm) (p<0.05). The addition of sacral screws made the iliac screw forces lower for some functional loads but higher for other functional loads, and resulted in an increase of intraoperative screw forces when attaching the rods onto these additional screws. When lateral offset connectors were used, the toggle moments were 16% and 25% higher, respectively for the left and right sides. Inserting iliac through the sacrum resulted in 17% lower toggle moment compared to insertion through the iliac crest. Cross-rod connectors had no significant effect on the intraoperative iliac screw forces. Postoperative functional loading had an important effect (additional 34% screw axial force and 18% toggle moment).

INTERPRETATION

It is possible to reduce the iliac screw loads by adapting instrumentation variables and strategies. Reducing the loads could decrease the risk of failure associated with iliac screw fixations.

Predicting Failure of Iliac Fixation in Neuromuscular Spine Deformity

STUDY DESIGN

Retrospective comparative cohort study.

OBJECTIVES

Identify whether there are patient or surgical risk factors to predict the probability of failure of iliac screw fixation after correction of neuromuscular scoliosis.

SUMMARY OF BACKGROUND DATA

There are high reported failure rates of pelvic fixation in long posterior spinal fusion (PSF) constructs to the sacrum for neuromuscular scoliosis.

METHODS

Patients aged 5 to 25 years, at a single institution, had PSF to the sacrum from 2001 to 2009 with pelvic fixation using iliac screws. Clinical data were retrospectively reviewed to identify patient and surgical variables related to surgery. Failure of iliac fixation was identified strictly as a broken screw, disengagement of the screw from the connector or the connector from the rod, or set plug failure. Lucency around the screws greater than 2 mm was recorded but not considered a failure. Variables were analyzed in a statistical model to identify predictors of failure.

RESULTS

A total of 108 patients met inclusion criteria; 100 (38 female and 62 male) had appropriate radiographs and minimum 2-year follow-up (average, 5.5 years). Coronal deformity correction averaged 59%. Most patients (89%) had fill of 6 of 8 possible distal fixation points composed of L4, L5, S1, and ilium bilaterally. Iliac screw failure occurred in 27 patients (27%). The initial single predictor statistical model identified 2 possible predictors of failure (patient: spastic tone; and surgical: absence of distal crosslink). In the multivariable model, spastic tone remained a predictor of failure (p = .0103), whereas absence of distal crosslink bordered on significance (p = .0516).

CONCLUSIONS

Iliac screw fixation failure is common in patients with long PSF constructs for neuromuscular scoliosis. Spastic tone is a risk factor for failure of pelvic fixation. A distal crosslink may protect against pelvic fixation failure. Alternative techniques for pelvic fixation should be studied in an attempt to improve the failure rates of iliac screw pelvic fixation.

Iliac screw placement in neuromuscular scoliosis using anatomical landmarks and uniplanar anteroposterior fluoroscopic imaging with postoperative CT confirmation

OBJECT

Neuromuscular scoliosis is a challenging pathology to treat. Surgical correction can involve long fusion constructs extending to the pelvis. The deformity inherent in these patients makes it difficult to obtain adequate lateral intraoperative radiographs for traditional image-guided placement of iliac screws.

METHODS

A clinical and radiographic assessment of 14 patients with neuromuscular spinal deformity was conducted. From 2007 to 2013, 12 of these patients (mean age 14.25 years, range 10-20 years) underwent long spinal instrumentation (mean 15 levels, range 10-18 levels) and fusion to the pelvis, and 2 underwent placement of a growing rod construct with iliac screw placement at a single institution. The average length of follow-up was 33.7 months (range 6-64 months). Iliac screws were placed after identifying the posterior superior iliac spine and using only anteroposterior fluoroscopy (view of the inlet of the pelvis), rather than the technique of direct palpation of the sciatic notch. The accuracy of iliac screw placement was assessed with routine postoperative CT.

RESULTS

A total of 12 patients had 24 screws placed as part of a long-segment fusion to the pelvis, and 2 patients had two iliac screws placed as part of a growing rod construct for neuromuscular scoliosis. There were no iliac screw misplacements, and no complications directly related to the technique of iliac screw placement. For cases of definitive fusion (n = 12), the average coronal Cobb angle of patients with neuromuscular spinal deformity measured 62° before surgery and 44.3° immediately after surgery. The average preoperative thoracic kyphosis and lumbar sagittal lordosis measured 37.3° and 60.7°, respectively. Immediately after surgery, the thoracic and lumbar angles measured 30° and 41.1°, respectively. At last follow-up, the average coronal Cobb angle was maintained at 45.1°, and the thoracic and lumbar sagittal angles were maintained at 32.8° and 45.3°, respectively.

CONCLUSIONS

A less invasive technique for iliac screw placement can be performed safely with a low likelihood of screw misplacement. This technique offers the biomechanical advantages of iliac fixation without the soft tissue exposure typically needed for safe screw insertion. The technique relies on identification of the posterior superior iliac spine and high quality anteroposterior fluoroscopic imaging for a view of the pelvic inlet.

Multiaxial high-modularity spinopelvis (HMSP) fixation device in neuromuscular scoliosis: a comparative study

PURPOSE

To compare radiological and clinical results in patients operated for neuromuscular scoliosis with pelvic fixation using high-modularity spinopelvic screw (HMSP) designed by authors.

METHODS

Of 54 patients with neuromuscular scoliosis, group 1 comprised of 27 patients with conventional pelvic fixation; and group 2 comprised of 27 patients using HMSP. Results were evaluated radiologically and functionally. We compared preoperative and postoperative complications, especially the loosening or breakage of spinopelvis fixation device, failure of fixation, and the change of shadow around the spinopelvis fixation device.

RESULTS

There was no difference of correctional power, preoperative average Cobb's angle of each group was 79.8 and 75 to postoperative 30.2 and 28.3 (P < 0.05). Pelvic obliquity improved from average 18.3°-8.9° in group I and average 24.3°-12.5° in group II (P < 0.05). However, there was no difference between two groups (P > 0.05). Average blood loss was 2,698 ml in group 1 and 2,414.8 ml in group 2 (P > 0.05). Average operative time was 360 min in group 1 and 332 min in group 2 (P = 0.30). There was no difference found between two groups regarding gait and functional evaluation. On the all cases of group 1 and 2, the change of shadow around the spinopelvis fixation device was observed. There was one case of the fracture of spinopelvis fixation device in group I.

CONCLUSION

There was no difference of Cobb's angle and correctional power between the groups using HMSP when compared with the group using standard spinopelvis fixation device. Therefore, HMSP can be used more effectively in case of neuromuscular scoliosis.

Resultado a largo plazo de las fusiones largas espinopelvicas en escoliosis: importancia de la edad, la capacidad de marcha y el tipo de fijación ilíaca

OBJETIVO: Conocer los factores que influyen en los fracasos instrumentales lumbosacros después de fusiones espinopélvicas largas. MÉTODO: Estudio retrospectivo de pacientes diagnosticados con escoliosis, tratados quirúrgicamente por vía posterior, realizándo se fusión espinopélvica de T2 o T3 a ilíaco, utilizando tornillos pediculares e ilíacos. Se analizaron los fracasos instrumentales y su asociación con diferentes parámetros clínicos y radiológicos. RESULTADOS: Se presentan 44 pacientes con edad promedio de 24 años, con diferentes etiologías. El valor promedio preoperatorio de la curva mayor era de 74,2º, y en la revisión final la corrección promedio fue 67%. El desequilibrio anteroposterior y la inclinación pélvica, la cifosis torácica, la lordosis lumbar y el desequilibrio lateral mejoraron significativamente en la revisión final. Hubo 41% de fracasos de instrumentación, todos a nivel lumbosacro. Se encontró asociación significativa con más fracasos instrumentales en mayores de 17 años y en los que tenían deambulación autónoma. En 24 pacientes, se utilizó un solo tornillo ilíaco bilateralmente y en 20 pacientes, dos o más. Los dos grupos tuvieron una incidencia similar de fracasos. En el grupo de dos o más tornillos solo existieron roturas de barras sin desanclajes, ni lisis. El uso de implantes intersomáticos de L3 a S1 o cerclajes sublaminares con una tercera barra disminuyó la incidencia de fracasos. CONCLUSIONES: En esta serie se presentaron un 41% de fracasos instrumentales, todos localizados a nivel lumbosacro. Los pacientes con capacidad de deambulación autónoma y mayores de 17 años presentaron significativamente más fallas instrumentales. En los que se realizó fusión intersomática L3-S1 o una tercera barra con cerclajes sublaminares, disminuyó la incidencia.

Operative treatment for spinal deformities in cerebral palsy

The higher the functional impairment, the more likely patients with cerebral palsy (cP) are to develop a scoliotic deformity. This is usually long-sweeping, C-shaped, and progressive in nature, since the causes of the deformity, such as muscular weakness, imbalance, and osteoporosis, persist through adulthood. In contrast to idiopathic scoliosis, not only is the spine deformed, the patient is also sick. This multimorbidity warrants a multidisciplinary approach with close involvement of the caregivers from the beginning. Brace treatment is usually ineffective or intolerable in light of the mostly stiff and severe deformities and the poor nutritional status. The pros and cons of surgical correction need to weighed up when pelvic obliquity, subsequent loss of sitting balance, pressure sores, and pain due to impingement of the rib cage on the ileum become issues. General risks of, for example, pulmonary or urogenital infections, pulmonary failure, the need for a tracheostoma, permanent home ventilation, and death add to the particular surgery-related hazards, such as excessive bleeding, surgical site infections, pseudarthrosis, implant failure, and dural tears with leakage of cerebrospinal fluid. The overall complication rate averages around 25 %. From an orthopedic perspective, stiffness, marked deformities including sagittal profile disturbances and pelvic obliquity, as well as osteoporosis are the main challenges. In nonambulatory patients, long fusions from T2/T3 with forces distributed over all segments, low-profile anchors in areas of poor soft tissue coverage (sublaminar bands, wires), and strong lumbosacropelvic modern screw fixation in combination with meticulous fusion techniques (facetectomies, laminar decortication, use of local autologous bone) and hemostasis can be employed to keep the rate of surgical and implant-related complications at an acceptably low level. Excessive posterior release techniques, osteotomies, or even vertebrectomies in cases of very severe short-angled deformity mostly prevent anterior one- or two-stage releases. Despite improved operative techniques and implants with predictable and satisfactory deformity corrections, the comorbidities and quality-of-life related issues demand a thorough preoperative, multidisciplinary decision-making process that takes ethical and economic aspects into consideration.

Correction of pelvic obliquity in neuromuscular spinal deformities using the "T construct": results and complications in a prospective series of 60 patients

BACKGROUND

We present the results of a prospective series of 60 patients treated for neuromuscular spinal deformities with an original spinopelvic construct using two sacral screws and two iliac screws. Clinical and radiological results obtained with this new surgical technique were studied and discussed according to the epidemiological data and relevant literature.

METHODS

From January 2008 to June 2010, the clinical data of every patient who underwent spinopelvic fixation for treatment of a neuromuscular spinal deformity were recorded prospectively.

RESULTS

Sixty patients were operated on during the study period. Spinal correction and fusion was performed by posterior approach. In six patients with a residual spinopelvic imbalance more than 15° on lateral preoperative bending films, an anterior release of the thoracolumbar junction was performed on the same day, before posterior correction. Preoperative pelvic obliquity (PO) ranged from 4° to 44° (mean 21.6°). Postoperative pelvic obliquity ranged from 0° to 14 (mean 4.6°). No significant loss of correction was noted at the last follow-up. One patient died 3 months after the initial procedure due to respiratory compromise. 11 patients had early postoperative infections of the posterior approach.

CONCLUSIONS

Despite a high rate of infectious complications, optimal correction of pelvic obliquity requires extension of spinal instrumentation to the pelvis. Spinopelvic fixation remains a difficult challenge in neurological patients with hypotrophy. We think that pelvic fixation with the "T construct" did provide effective and improved spinal stabilization in these patients, while reducing the need for a postoperative cast or brace. As a result, patients had a favourable postoperative course with early mobilization and return to a comfortable sitting position.

Posterior second sacral alar iliac screw insertion: anatomic study in a Chinese population

OBJECTIVE

To provide radiographic parameters for optimal placement of posterior second sacral alar iliac (S2AI) screw for instrumentation and fusion of scoliosis to the second sacral level in a Chinese population.

METHODS

S2AI screw trajectories were mapped on three-dimensional computed tomography (3DCT) reconstructions of 60 normal adult pelvises. 1 mm inferior and 1 mm lateral to the S1 dorsal foramen were chosen as the entry point, and ideal S2AI screw trajectories were explored by rotating and cutting the 3D pelvis, ensuring that the trajectories were of maximum length and width. The directions and depth of these determined trajectories were then measured.

RESULTS

The ideal S2AI screw trajectories could be found in each pelvis. The left and right screw trajectory parameters for males were shown as follows: angulation was L 29.15 ± 8.60° vs. R 29.96 ± 8.28° (p = 0.286) caudally in the sagittal plane and L 36.49 ± 3.14° vs. R 37.16 ± 3.14° (p = 0.165) laterally in the transverse plane. The maximal and intrasacral lengths of trajectory were L 121.25 ± 8.33 vs. R 120.63 ± 7.54 mm (p = 0.460) and L 26.20 ± 3.31 vs. R 26.92 ± 4.76 mm (p = 0.268). The entry point was L 28.87 ± 3.33 vs. R 29.79 ± 3.55 mm (p = 0.186) lateral to the second sacral midline, and L 44.14 ± 11.87 vs. R 43.89 ± 12.53 mm (p = 0.687) underneath the skin. The trajectories for females were more caudal (L: 34.50 ± 6.56° vs. 29.15 ± 8.60°, p = 0.009; R: 35.72 ± 7.53° vs. 29.96 ± 8.28°, p = 0.007) in the sagittal plane, but the lateral angulation in the transverse plane showed no difference between genders (p > 0.05). The female iliac medullar cavities were obviously narrower than those of males (L: 14.76 ± 2.46 vs. 16.98 ± 3.52, p = 0.006; R: 14.94 ± 2.60 vs. 17.00 ± 2.81, p = 0.005). Although the average maximal length of trajectories for females were about 5 mm shorter than those of males, intrasacral length were equal to those of males. Furthermore, both the distance from entry point to the S2 midline and skin in the transverse plane showed no difference between genders.

CONCLUSION

The feasibility to insert S2AI screws to the sacrum and ilium in an Asian population along with the ideal entry angle and length of trajectory were identified for clinical practice.

Treatment of spine deformity in neuromuscular diseases

Surgical management of spinal deformity in neuromuscular diseases (NMDs) often requires a multidisciplinary approach beginning in the preoperative surgical planning period, owing to concomitant restrictive lung disease and cardiomyopathy in selected NMD conditions. The need for thorough and thoughtful discussions must occur with the family and other caregivers before any scheduled surgery. The decision to proceed with spinal instrumentation may alter functional abilities in weak and marginally ambulatory NMD patients. With care and treatment involving a multidisciplinary team, proper planning, and support, patients will likely experience rewarding outcomes and improved quality of life.

Prevalence of complications in neuromuscular scoliosis surgery: a literature meta-analysis from the past 15 years

PURPOSE

Our objectives were primarily to review the published literature on complications in neuromuscular scoliosis (NMS) surgery and secondarily, by means of a meta-analysis, to determine the overall pooled rates (PR) of various complications associated with NMS surgery.

METHODS

PubMed and Embase databases were searched for studies reporting the outcomes and complications of NMS surgery, published from 1997 to May 2011. We focused on NMS as defined by the Scoliosis Research Society's classification. We measured the pooled estimate of the overall complication rates (PR) using a random effects meta-analytic model. This model considers both intra- and inter-study variation in calculating PR.

RESULTS

Systematic review and meta-analysis were performed for 68 cohort and case-control studies with a total of 15,218 NMS patients. Pulmonary complications were the most reported (PR = 22.71 %) followed by implant complications (PR = 12.51 %), infections (PR = 10.91 %), neurological complications (PR = 3.01 %) and pseudoarthrosis (PR = 1.88 %). Revision, removal and extension of implant had highest PR (7.87 %) followed by malplacement of the pedicle screws (4.81 %). Rates of individual studies have moderate to high variability. The studies were heterogeneous in methodology and outcome types, which are plausible explanations for the variability; sensitivity analysis with respect to age at surgery, sample size, publication year and diagnosis could also partly explain this variability. In regard to surgical complications affiliated with various surgical techniques in NMS, the level of evidence of published literature ranges between 2+ to 2-; the subsequent recommendations are level C.

CONCLUSION

NMS patients have diverse and high complication rates after scoliosis surgery. High PRs of complications warrant more attention from the surgical community. Although the PR of all complications are affected by heterogeneity, they nevertheless provide valuable insights into the impact of methodological settings (sample size), patient characteristics (age at surgery), and continual advances in patient care on complication rates.

Pelvic fixation for neuromuscular scoliosis deformity correction

Pelvic fixation is most frequently indicated in the pediatric population for the treatment of neuromuscular scoliosis with significant pelvic obliquity. Neuromuscular scoliosis surgery is associated with a high risk of complications, and this is further increased by extension of fusion to the sacrum. Numerous techniques have been described for pelvic fixation associated with a long spine fusion each with its own set of specific benefits and risks. This article reviews the contemporary surgical techniques of pelvic fixation used to extend a spine fusion to the sacrum and pelvis focusing on the management of neuromuscular scoliosis, including their biomechanical rationale, results, and complications.

Results and complications after spinal fusion for neuromuscular scoliosis in cerebral palsy and static encephalopathy using luque galveston instrumentation: experience in 93 patients

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To evaluate the results of spine fusion for neuromuscular scoliosis in cerebral palsy and static encephalopathy, using Luque-Galveston technique, with emphasis on the early and late complications, especially those increasing the hospital stay or requiring additional surgery.

SUMMARY OF BACKGROUND DATA

There are numerous studies in the literature on the treatment of neuromuscular scoliosis using Luque-Galveston instrumentation analyzing the results and complications. Most series are small and evaluate some of the complications, with none evaluating all the early and late complications and none assessing the impact of the complication on length of hospitalization or the need for additional surgical intervention.

METHODS

This was a retrospective review of a consecutive series of patients operated on for neuromuscular scoliosis in cerebral palsy and static encephalopathy with Luque-Galveston instrumentation at 1 institution from January 1997 to December 2003. Ninety-three patients were identified.

RESULTS

The average age at surgery was 14.3 years, with an average age at follow-up of 18.2 years, and an average follow-up of 3.8 years. The mean preoperative scoliosis was 72° with correction postoperatively to a mean of 33°, maintained at 36° at final follow-up. There were 83 early complications in 54 patients, for a complication rate of 58% of patients for the entire study. There were no perioperative deaths or neurological complications. There was only 1 deep wound infection, for an infection rate of 1.1%. Patients with 1 complication had a longer length of stay, 9 versus 7 days, the difference being statistically significant (Mann-Whitney U test, P < 0.001). Two patients required reoperation during the initial hospitalization (1.1%): 1, one for infection and 1 for proximal hook cutout and proximal junction kyphosis. There were a total of 81 late complications in 44 patients, for a late complication rate of 47% of patients for the entire study. The majority of the complications were minor, not requiring additional care or surgery. Seven patients had a pseudarthrosis (7.5%), presenting at an average of 30 months postoperatively. Eight patients underwent 9 procedures for late complications: 5 for repair of a pseudarthrosis, 3 for removal of a prominent iliac screw, and 1 for superior junctional kyphosis. All the pseudarthrosis repairs were solid at follow-up.

CONCLUSION

Spinal fusion in neuromuscular scoliosis with Luque-Galveston technique is a safe and effective procedure. Any early complication increased the length of stay, with a low rate of reoperation during the hospitalization. The majority of late complications were minor, not requiring additional care. Pseudarthroses were detected late and were the main reason for additional surgery.

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.

A new pelvic rod system for the surgical correction and fixation of pelvic obliquity in pediatric neuromuscular scoliosis

PURPOSE

To describe surgical outcomes using the new device in pediatric neuromuscular scoliosis.

METHODS

All patients with neuromuscular disorders requiring surgery with pelvic fixation for the correction of scoliosis in the period 2002-2009 were operated by the new pelvic rod fixation device. Coronal and sagittal alignment before and after surgery until the latest follow-up were evaluated by standard X-rays. Intraoperative and postoperative complications were recorded.

RESULTS

All 18 study patients (mean age at surgery 15 years, range 10-27) achieved solid fusion at a mean follow-up of 41 months. The coronal Cobb angle improved from 82° ± 31° (range 36-168) to 33° ± 25° at the last follow-up (range 9-95 months) (P < 0.0001). Pelvic obliquity improved from 19° ± 6° (range 10-30) to 5° ± 5° (range 0-14) (P < 0.0001). Early complications included pneumonia, urinary tract infection, disseminated intravascular coagulation (DIC), and hypovolemic shock. Three patients required debriding and received prolonged antimicrobial therapy for deep wound infection (none required implant removal). At the latest follow-up, no patient complained of lumbar pain or worsening of ambulatory status or level of activity.

CONCLUSION

Surgery employing the new pelvic rod fixation device allowed solid fusion and fixation with significant correction of multiplanar deformity, but the complication rate was high.

Surgical management of spinal deformities in cerebral palsy. A review

Cerebral palsy (CP) spinal deformities encompass a spectrum of deformities that are often initially treated nonoperatively, only to result in progression of scoliotic curves and further morbidity. Various surgical interventions have been devised to address the progressive curvature of the spine. This endeavor cannot be taken lightly and at times can be encumbered by prior treatments such as the use of baclofen pumps or dorsal rhizotomies. Care of these patients requires a multidisciplinary approach and comprehensive preoperative and postoperative management, including nutritional status, orthopedic assessment of functional level with specific emphasis on the hips and pelvic obliquity, and wheelchair modifications. The surgical techniques in CP scoliosis have progressively evolved from the classic Luque-Galveston fixation methods, the use of unit rods, and lately the use of pedicle screws, to modern sacropelvic fixation. With the latter method, the spinal deformity in patients with CP can usually be almost completely corrected.

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.

Treatment and complications in flaccid neuromuscular scoliosis (Duchenne muscular dystrophy and spinal muscular atrophy) with posterior-only pedicle screw instrumentation

Literature has described treatment of flaccid neuromuscular scoliosis using different instrumentation; however, only one article has been published using posterior-only pedicle screw fixation. Complications using pedicle screws in paralytic neuromuscular scoliosis has not been described before. To present results and complications with posterior-only pedicle screws, a retrospective study was carried out in 27 consecutive patients with flaccid neuromuscular scoliosis (Duchenne muscular dystrophy and spinal muscular atrophy), who were operated between 2002 and 2006 using posterior-only pedicle screw instrumentation. Immediate postoperative and final follow-up results were compared using t test for Cobb angle, pelvic obliquity, thoracic kyphosis and lumbar lordosis. Perioperative and postoperative complications were noted from the hospital records of each patient. Complications, not described in literature, were discussed in detail. Average follow-up was 32.2 months. Preoperative, immediate postoperative and final follow-up Cobb angle were 79.8 degrees , 30.2 degrees (63.3% correction, p < 0.0001) and 31.9 degrees , respectively; and pelvic obliquity was 18.3 degrees , 8.9 degrees (52% correction, p < 0.0001) and 8.9 degrees . Postoperative thoracic kyphosis remained unchanged from 27.6 degrees to 19.9 degrees (p = 0.376); while lumbar lordosis improved significantly from +15.6 degrees to -22.4 degrees lordosis (p = 0.0002). Most patients had major to moderate improvement in postoperative functional and ambulatory status compared to the preoperative status. Thirteen (48.1%) perioperative complications were noted with five major complications (four respiratory in the form of hemothorax or respiratory failure that required ventilator support and one death) and eight minor complications (three UTI, two atelectasis, two neurological and one ileus). Postoperatively, we noted complications, such as coccygodynia with subluxation in 7, back sore on the convex side in 4 and dislodging of rod distally in 1 patient making a total of 12 (44.4%) postoperative complications. Of 12 postoperative complications, 6 (50%) required secondary procedure. We conclude that although flaccid neuromuscular scoliosis can be well corrected with posterior-only pedicle screw, there is a high rate of associated complications.

Spinopelvic fixation with iliosacral screws in neuromuscular spinal deformities: results in a prospective cohort of 62 patients

PURPOSE

The results of a prospective series of 62 patients treated for neuromuscular spinal deformities with spinopelvic fixation using iliosacral screws are presented and discussed.

METHODS

Sixty-two consecutive patients diagnosed with neuromuscular disorders were prospectively included. Pelvic obliquity and other angular parameters were measured.

RESULTS

Mean age was 15.2 years (11.9 to 19.2 years). Spinal deformity was a thoracolumbar curve in 36 cases, a lumbosacral curve in 14 cases, a lumbar curve in four cases, and a combined thoracic and lumbar curve in eight cases. Lumbo-pelvic correction was done using two different strategies. In 15 patients with a normal frontal spinopelvic balance, the two rods were extended directly down to the iliosacral screws. In 47 patients with pelvic obliquity, iliosacral screws were linked to two short rods. The correction was then corrected by distraction and contraction maneuvers applied between the long and short rods. Postoperative angular parameters showed a good correction of spinal deformity in both groups. Patients with preoperative pelvic obliquity had a satisfactory and stable correction at final follow-up.

CONCLUSIONS

The technique of pelvic fixation using iliosacral screws and connectors reduce difficulties and operative time due to the complicated three-dimensional bending of the rods for proper placement within the ilium. In patients with preoperative pelvic imbalance, a powerful pelvic anchorage as the iliosacral fixation allowed to use intraoperative reduction maneuvers. Despite the high rate of infectious complications in our patients, we think that our technique provided effective and improved spinal correction for patients with neuromuscular scoliosis.

Evaluation of pelvic fixation in neuromuscular scoliosis: a retrospective study in 55 patients

The literature has described different indications for pelvic fixation in neuromuscular scoliosis. We retrospectively evaluated changes in pelvic obliquity for a minimum of two years among three groups: group I (initial pelvic obliquity >15 degrees; with pelvic fixation), group II (initial pelvic obliquity >15 degrees; without pelvic fixation), and group III (initial pelvic obliquity <15 degrees; without pelvic fixation). We used iliac screws for pelvic fixation in group I. There was significant postoperative improvement (p < 0.0001) in Cobb's angle and pelvic obliquity. There was no significant loss of correction in Cobb's angle, thoracic kyphosis, and lumbar lordosis among all three groups; however, group II showed significant correction loss in pelvic obliquity compared to groups I and III at final follow-up (p < 0.0001). Our results indicate that patients who have pelvic obliquity >15 degrees require pelvic fixation to maintain the correction and balance over time while obliquity <15 degrees does not require pelvic fixation.