What's New in Pediatric Spine Growth Modulation and Implant Technology for Early-Onset Scoliosis?

A novel approach to surgical treatment of adolescent idiopathic scoliosis in skeletally immature patients

Purpose

Describe the surgical technique and experience using the LSZ growing system in skeletally immature patients for two-stage surgical treatment of adolescent idiopathic scoliosis (AIS).

Methods

Eleven skeletally immature patients who underwent two-stage surgical treatment of AIS in our center were retrospectively analyzed. Patients initially treated with the LSZ growing system were observed for an average of 40.5 months (range 23-64 months) and for 4 years after planned replacement of the LSZ growing system with a standard pedicle screw system.

Results

The average preoperative angle of the main thoracic curve was 64.55 ± 3.21°, and that of the lumbar curve was 46 ± 5.52°. After instrumentation using the LSZ growing system, the thoracic curve was corrected to 17.63 ± 5.14°, and the lumbar curve to 9.2 ± 5.45°. The correction percentages were 72.52 ± 8.35 and 80.59 ± 10.77, respectively. After planned replacement of the LSZ system with a pedicle screw system, the angle of the thoracic curve changed to 11.45 ± 4.84°, and the lumbar curve to 6.4 ± 4.72°. The percentages of final correction were 82,1 ± 7,91 and 85,64 ± 5,47, respectively. The difference in the "LSZ growth coefficient" was 0.063 ± 0.037, which indicates continued growth of the spine along the instrumented region. None of the patients had neurological or infectious complications.

Conclusion

Our study demonstrates the safety and effectiveness of 2-stage treatment of AIS using the LSZ system, which allows for spine growth during the period between stages.

Comparison of Relative Value Units and 30-Day Outcomes Between Primary and Revision Pediatric Spinal Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to compare the relative value units (RVUs) and 30-day outcomes between primary and revision pediatric spinal deformity (PSD) surgery.

SUMMARY OF BACKGROUND DATA

PSD surgery is frequently complicated by the need for reoperation. However, there is limited literature on physician reimbursement rates and short-term outcomes following primary versus revision spinal deformity surgery in the pediatric population.

MATERIALS AND METHODS

This study utilizes data obtained from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) Pediatric database. Patients between 10 and 18 years of age who underwent posterior spinal deformity surgery between 2012 and 2018 were included. Univariate and multivariate regression were used to assess the independent impact of revision surgery on RVUs and postoperative outcomes, including 30-day readmission, reoperation, morbidity, and complications.

RESULTS

The study cohort included a total of 15,055 patients, with 358 patients who underwent revision surgery. Patients in the revision group were more likely to be younger and male sex. Revision surgery more commonly required osteotomy (13.7% vs. 8.3%, P =0.002).Univariate analysis revealed higher total RVUs (71.09 vs. 60.51, P <0.001), RVUs per minute (0.27 vs. 0.23, P <0.001), readmission rate (6.7% vs. 4.0%, P =0.012), and reoperation rate (7.5% vs. 3.3%, P <0.001) for the revision surgery group. Morbidity rates were found to be statistically similar. In addition, deep surgical site infection, pulmonary embolism, and urinary tract infection were more common in the revision group. After controlling for baseline differences in multivariate regression, the differences in total RVUs, RVUs per minute, reoperation rate, and rate of pulmonary embolism between primary and revision surgery remained statistically significant.

CONCLUSIONS

Revision PSD surgery was found to be assigned appropriately higher mean total RVUs and RVUs per minute corresponding to the higher operative complexity compared with primary surgery. Revision surgery was also associated with poorer 30-day outcomes, including higher frequencies of reoperation and pulmonary embolism.

LEVEL OF EVIDENCE

Level III.

The Effect of Surgeon Experience on Outcomes Following Growth Friendly Instrumentation for Early Onset Scoliosis

BACKGROUND

The purpose of this study was to utilize a multicenter, multisurgeon cohort to assess the effect of surgeon experience on outcomes of growth friendly instrumentation (GFI) in early onset scoliosis (EOS). We hypothesized that unplanned return to the operating room (UPROR), estimated blood loss (EBL), and surgical time would be greater amongst early career surgeons (ECSs) when compared with advanced career surgeons (ACSs).

METHODS

An international pediatric spine database was queried for patients ages 2 to 10 years treated by posterior distraction-based GFI with at least of 2-year follow up. Two groups were created for analysis based on surgeon experience: ECSs (with ≤10 y of experience) and ACSs (with >10 y of experience). The primary outcome was UPROR. Additional outcomes included: operating room time, EBL, neurological deficits, infection rate, hardware failure, and the Early Onset Scoliosis Questionnaire (EOSQ-24). Subgroup analysis was performed for further assessment based on procedure type, superior anchor type, etiology, and curve severity.

RESULTS

A total of 960 patients met inclusion criteria including 243 (25.3%) treated by ECS. Etiology, sex, superior anchor, and EOSQ-24 scores were similar between groups (P>0.05). There were no clinically significant differences in patient age or preoperative major coronal curve. UPROR (35.8% vs. 32.7%, P=0.532), infection (17.0% vs. 15.6%, P=0.698), operating room time (235 vs. 231 min, P=0.755), and EBL (151 vs. 155 mL, P=0.833) were comparable between ECS and ACS groups. The frequency of having at least 1 complication was relatively high but comparable among groups (60.7% vs. 62.6%, P=0.709). EOSQ-24 subdomain scores were similar between groups at 2-year follow-up (P>0.05). Subgroup analysis revealed that ECS had increased surgical time compared with ACS in severe curves >90 degrees (270 vs. 229 min, P=0.05).

CONCLUSIONS

This study represents the first multicenter assessment of surgeon experience on outcomes in EOS. Overall, surgeon experience did not significantly influence UPROR, complication rates, EBL, or surgical time associated with GFI in this cohort of EOS patients.

LEVEL OF EVIDENCE

Level III.

Feasibility of microwave ablation of the vertebral growth plate for spine growth regulation: a preliminary study

PURPOSE

To explore the feasibility of microwave ablation (MWA) of the vertebral growth plate as a minimally invasive treatment for early-onset scoliosis.

MATERIALS AND METHODS

One side of the L1-L3 vertebral growth plates were ablated using different MWA powers. Ablation safety and size were examined. Subsequently, L1-L3 vertebral growth plates were ablated on one side for 40 s at 20 W. At 2, 4, and 6 weeks after the ablation, growth changes of the spine were observed.

RESULTS

No piglets died during and after ablation, and all had modified Tarlov Grade 5. The safe MWA time (time for safely ablating the vertebral growth plate) was 17.0 ± 1.5 s at 50 W, 23.0 ± 2.3 s at 40 W, 31.0 ± 3.1 s at 30 W, 47.0 ± 3.7 s at 20 W, 70.0 ± 4.2 s at 15 W, and 158.0 ± 5.0 s at 10 W. With power <15 W, the vertebral growth plate could not be effectively ablated within the safe ablation time. Within the safe ablation times, the MWA size on hematoxylin and eosin slices on a transverse diameter was between 7 and 10 mm; and that on longitudinal diameter was mainly determined by the ablation needle length. Moreover, the growth plate and annulus fibrosus on the ablated side grew poorly over time, the vertebral body showed significant wedge-shaped changes, and the spine showed significant unbalanced growth.

CONCLUSION

MWA of the vertebral growth plate can be performed safely when accompanied with appropriate thermometry, and could be a new minimally invasive strategy in regulating spine growth.

Revision risk after pediatric spinal deformity surgery: a nationwide study with 2-year follow-up

BACKGROUND CONTEXT

Revision risk after pediatric spine surgery is not well established and varies between deformity etiologies.

PURPOSE

To report the 2-year revision risk following surgery for primary pediatric spinal deformity in a nationwide cohort and to evaluate potential risk factors and reasons for revision surgery.

DESIGN

Retrospective nationwide cohort study.

PATIENT SAMPLE

A national registry study of all pediatric spinal deformity patients undergoing surgery during 2006-2015 (n=1310).

OUTCOME MEASURES

Two-year revision risk.

METHODS

All patients ≤21 years of age undergoing spinal deformity surgery in Denmark during 2006-2015 were identified by procedure and diagnosis codes in the Danish National Patient Registry (DNPR). Data on revision surgery were retrieved from the DNPR. Patients were categorized in six groups according to etiology. Medical records were reviewed for reason for revision in all patients. Potential risk factors for revision were assessed with multiple logistic regression analyses and included age, etiology, sex, Charlson comorbidity index (CCI), and growth-preserving treatment.

RESULTS

Patients were categorized according to etiology: idiopathic deformity (53%), neuromuscular deformity (23%), congenital/structural deformity (9%), spondylolisthesis (7%), Scheuermann's kyphosis (5%), and syndromic deformity (3%). Of 1,310 included patients, 9.2% underwent revision surgery within 2 years and 1.5% was revised more than once. Median time to revision was 203 (interquartile range 35-485) days. The multivariable logistic regression found significantly higher odds ratio (OR) for revision in patients with growth-preserving treatment (OR=5.1, 95% confidence interval [CI] 2.6-10.1), congenital deformity (OR=2.7, 95% CI 1.3-5.3), spondylolisthesis (OR=3.5, 95% CI 1.9-6.7), Scheuermann kyphosis (OR=3.9, 95% CI 1.9-8.3), and CCI score ≥3 (OR=2.5 95% CI 1.1-5.6). The most common reason for revision was implant failure (32.5%) followed by residual deformity and/or curve progression (15.8%).

CONCLUSIONS

In this nationwide study, the 2-year revision risk after primary pediatric spinal deformity surgery is 9.2%. Risk factors for revision are etiology of congenital deformity, spondylolisthesis, Scheuermann kyphosis as well as patients with growth-preserving treatment and higher CCI. The most common reason for revision is implant failure.

Characterizing Use of Growth-friendly Implants for Early-onset Scoliosis: A 10-Year Update

BACKGROUND

Growth-friendly treatment of early-onset scoliosis (EOS) has changed with the development and evolution of multiple devices. This study was designed to characterize changes in the use of growth-friendly implants for EOS from 2007 to 2017.

METHODS

We queried the Pediatric Spine Study Group database for patients who underwent index surgery with growth-friendly implants from July 2007 to June 2017. In 1298 patients, we assessed causes of EOS; preoperative curve magnitude; age at first surgery; patient sex; construct type; lengthening interval; incidence of "final" fusion for definitive treatment; and age at definitive treatment. α=0.05.

RESULTS

From 2007 to 2017, the annual proportion of patients with idiopathic EOS increased from 12% to 33% (R=0.58, P=0.006). Neuromuscular EOS was the most common type at all time points (range, 33% to 44%). By year, mean preoperative curve magnitude ranged from 67 to 77 degrees, with no significant temporal changes. Mean (±SD) age at first surgery increased from 6.1±2.9 years in 2007 to 7.8±2.5 years in 2017 (R=0.78, P<0.001). As a proportion of new implants, magnetically controlled growing rods increased from <5% during the first 2 years to 83% in the last 2 years of the study. Vertically expandable prosthetic titanium ribs decreased from a peak of 48% to 6%; growth-guidance devices decreased from 10% to 3%. No change was seen in mean surgical lengthening intervals (range, 6 to 9 mo) for the 614 patients with recorded lengthenings. Final fusion was performed in 88% of patients who had undergone definitive treatment, occurring at a mean age of 13.4±2.4 years.

CONCLUSIONS

From 2007 to 2017, neuromuscular EOS was the most common diagnosis for patients treated with growth-friendly implants. Patient age at first surgery and the use of magnetically controlled growing rods increased during this time. Preoperative curve magnitude, traditional growing rod lengthening intervals, and rates of final fusion did not change.

LEVEL OF EVIDENCE

Level II.

Unplanned return to OR (UPROR) for children with early onset scoliosis (EOS): a comprehensive evaluation of all diagnoses and instrumentation strategies

STUDY DESIGN

Retrospective analysis of a prospectively collected multicenter database.

OBJECTIVES

Our goal was to study unplanned return to the OR (UPROR, a postoperative complication that could not be treated without an additional anesthetic) as a function of C-EOS diagnosis and implant type. Growing concerns over the impact of multiple anesthetic events on the young brain have focused attention on limiting UPROR in early onset scoliosis (EOS).

METHODS

We studied all patients with a diagnosis of EOS who had surgical implantation of growing instrumentation from October 4, 2010, to September 27, 2015, with a minimum 2-year follow-up. Among the complications requiring surgical treatment (revision for implant or anchor failure, infection, or implant removal), we analyzed all UPROR events-those that required a separate anesthetic (could not be treated as part of a planned surgical lengthening) within the first 2 years after initial implantation. UPROR was analyzed by diagnosis, deformity type, and implant strategy using the C-EOS classification.

RESULTS

A total of 369 patients met inclusion criteria. Eighty-five of the 369 (23%) required unplanned trips to the operating room for various reasons. The C-EOS group at highest risk of an unplanned trip to the operating room is the hyperkyphotic neuromuscular (M3+, 14/85) cohort, followed closely by the congenital (C3N, 9/85) and neuromuscular (M3N, 8/85) groups with normal sagittal profiles and Cobb angles between 50° and 90°. Implant strategy was significantly related to risk of UPROR (p = .009; Table 1), with traditional implants (vertically expandable prosthetic titanium rib/traditional growing rod) being less likely to have an UPROR event.

CONCLUSIONS

Growing instrumentation to treat EOS, when considered comprehensively, results in a true unplanned reoperation rate within 2 years of implantation of 23% (85/369). UPROR events are more common with certain C-EOS groups (hyperkyphotic neuromuscular deformities) and implant strategies. Families should be counseled that unplanned anesthetics are common with any implant strategy available today.

LEVEL OF EVIDENCE

Level III, therapeutic.

Minimizing Spine Autofusion With the Use of Semiconstrained Growing Rods for Early Onset Scoliosis in Children

BACKGROUND

A new growing rod (GR) design, the semiconstrained growing rod (SCGR), with the added advantage of axial rotation freedom within the components, has been introduced at our center which has been shown to be growth friendly. We hypothesize that the SCGR system would reduce autofusion in vivo, thereby maximizing the coronal plane correction, T1-S1 growth, and the final correction achieved at definitive fusion for children with an early onset scoliosis.

METHODS

In total, 28 patients had either single or dual 5.5 mm diameter SCGR placed minimally invasively through a submuscular approach. Surgical lengthening procedures occurred approximately every 6 months until the definitive fusion procedure was performed for 18 patients. Scoliosis, kyphosis, and lordosis angles, T1-S1 trunk length, and any complications encountered were evaluated.

RESULTS

For the full cohort, before GR insertion, the mean major Cobb curve angle was 72.4 degrees (SD, 18.8; range, 45 to 120), mean T1-S1 trunk length was 282 mm (SD, 59; range, 129 to 365), and at the latest follow-up (mean 6.9 y, SD 3.3, range 2.0 to 13.0), 38.8 degrees (SD, 17.5; range 10 to 90) and 377 mm (SD, 62; range, 225 to 487), respectively. For the subset of 18 patients who have had their final instrumented fusion surgery, the definitive surgery procedure alone produced a correction of the major Cobb curve angle by mean 20.3 degrees (SD, 16.1; P<0.0001), and an increase in the T1-S1 trunk length of mean 31.7 mm (SD, 23.1; P<0.0001). There were 14 complications involving 11 of the 28 patients, giving rise to 5 unplanned surgical interventions and 1 case where GR treatment was abandoned.

CONCLUSIONS

SCGR patients exhibited statistically significant increase in T1-S1 trunk length and statistically significant decrease in the severity of scoliosis over the course of GR treatment and again, importantly, with the definitive fusion surgery, suggesting that autofusion had been minimized during GR treatment with relatively low complication rates.

LEVEL OF EVIDENCE

Level IV-case series.