Adolescent Idiopathic Scoliosis, Skeletal Maturity, Surgery—Discussion, Conclusion

Meeting highlight from the American Association of Orthopaedic Surgeons 2017 Annual Meeting

This is a continuation of Surgery for Adolescent Idiopathic Scoliosis Patients After Skeletal Maturity: Now or Later?, specifically the statistical analysis, that was presented by Baron S. Lonner, MD, at the American Association of Orthopaedic Surgeons 2017 Annual Meeting.

Discussion
A common clinical scenario for the spine surgeon who treats adolescent idiopathic scoliosis is the presentation of a skeletally mature patient with moderately severe curvature who meets radiographic criteria for surgical intervention but is asymptomatic.
Face of a clock“Should we send our daughter to you for surgery now, or should we consider waiting until symptoms develop or curve progression occurs?” This is essentially a question of natural history of the disease. Not uncommonly, in the current healthcare milieu in which the patient and family are encouraged to question treatment alternatives and their rationale, discussions on the merits of an intervention in the patient without pain, pulmonary dysfunction, or other disability, are undertaken.

Nonoperative treatment modalities such as Scoliosis Specific Physical Therapy (eg, Schroth method) and aggressively marketed chiropractic treatment have exploded and left families with options, even in the absence of a high level of medical evidence.

Surgical correction of the skeletally mature adolescent often evokes fear among family members as to the possibility of complications, especially paralysis. The question frequently asked by parents is: “Should we send our daughter to you for surgery now, or should we consider waiting until symptoms develop or curve progression occurs?” This is essentially a question of natural history of the disease and its subsequent treatment.

Dr. Lonner and colleagues set out to provide data that can be used to counsel families and inform surgical recommendations on the nature of the surgical intervention for the patient with adolescent idiopathic scoliosis vs the patient who has lived for a decade or more beyond adolescence and presents for surgery as an adult. To begin to answer this question, Dr. Lonner’s team used two prospective multicenter registries: one pediatric and one adult.

The data shows that the average patient with adult idiopathic scoliosis in the study, nearly 30 years older than their 15 years-of-age counterparts with adolescent idiopathic scoliosis, has experienced a significantly greater impact on quality of life than the adolescent by the time surgery is performed.

Gender-age normalized scores in all domains of the SRS were less for the adult prior to surgery. Due to the deficit in quality of life, greater improvements in pain, function, and total score domains were found in the adult cohort. Despite this, 2-year postoperative pain, image, function, and total domain scores were less for adult than adolescent idiopathic scoliosis.

The minimal clinically important difference for both cohorts was achieved in the pain, image, function, and total scores as a result of surgery. What is unknown is the longevity of those outcomes beyond 2 years.

The data shows the patient with adult idiopathic scoliosis begins with worse quality of life and improves to a greater extent in most domains than their adolescent counterpart but remains at a lower level in those same domains as preoperatively.

Consistent with the methodology of the study, patients with adult idiopathic scoliosis harbored larger curves at the time of surgery by just over 8-degrees (58.3-degrees vs 49.9-degrees). Despite this, percent correction was similar for both groups (~62%) as were final curve magnitudes (21.8-degrees vs 19-degrees). This finding was not expected. Larger cohorts are needed; however, to age-stratify and assess differences in radiographic corrections by age group.

A relatively conservative estimation of progression was chosen so as to not overstate the true observed natural history of progression. Weinstein et al, in their landmark natural history study, reported mean annual curve progression over 40 years of 0.74-degrees per year for thoracic curves, and 0.56-degrees per year for thoracolumbar curves.

Dr. Lonner’s team used a factor 0.3-degree annual progression for the first 10 years, and 0.5-degrees per year thereafter. They also took into account a gradual increase in kyphosis that takes place with aging as reported by Fon et al. They understood that this modeling is imperfect, but it represents, they believed, a fair estimate of possible curve progression.

Prospective, randomized studies are difficult to perform in this population as families seeking surgical intervention for the patient with adolescent idiopathic scoliosis would be asked to forego surgery in favor of allowing natural history to play out over decades. Others would be asked to consent to surgery even if this would not be desirable.

In addition, a prospective study would require decades to complete. This methodology allows for estimation of the natural history and a first look at the question of differences in the quality of life and surgical experience for the patient with adult vs adolescent idiopathic scoliosis.

As the investigators hypothesized, operative morbidity was significantly greater for patients with adult than for those with adolescent idiopathic scoliosis. Fusions were 3.5 levels longer in adult idiopathic scoliosis patients and fusion to the pelvis was required in 36%. In addition, nearly 30% of patients with adult idiopathic scoliosis underwent combined anterior-posterior surgery.

Operative time was longer (414 vs 281 minutes; P=.0001), blood loss was nearly twice as much (approximately 1400 vs 700 mL; P=.0027), and blood loss as a percentage of blood volume (35.1 vs 20.3; P=.0027), and length of stay (6.3 vs 5.3 days; P=.0043) were all greater for patients with adult vs adolescent idiopathic scoliosis.

Though the differences in operative parameters became less evident between the two cohorts after stratified by Lenke curve type due to reduced sample size, they were largely abolished with normalization by levels fused. Nevertheless, the trends were instructive and warrant further study with larger cohorts.

Dr. Lonner’s team did not have data consistently available but blood transfusion requirements were likely greater for the adult study group given the higher estimated blood loss as a percentage of blood volume. Longer fusions in adults, when not extended to the sacrum, may also result in a self-fulfilling prophecy of distal segment disc degeneration, potentially due to increased intradiscal pressures and fewer motion segments available to preserve motion.

Though the team found an increased number of fusion levels as well as fusion to the sacrum with pelvic fixation in the adults, the question on longevity of the fusion in patients with adolescent idiopathic scoliosis was not answered, that is, “Will distal disc degeneration occur at some point, necessitating later extension of the fusion distally?”

Longer-term follow-up is required to begin to answer this question. Also, fusionless corrective surgery is beginning to find its way into the armamentarium of the pediatric scoliosis surgeon and may exert a profound impact on the fate of nonoperated segments compared to fusion approaches.

Perhaps the most compelling information for families was the data on complications. Major complication rates of 25% were found for the adult vs 5.4% for the adolescent idiopathic scoliosis groups. Four of 28 neurological complications occurred in adult and one of 56 in adolescent idiopathic scoliosis, none of which required reoperation.

Both groups encountered one case of implant loosening, one patient in the adult group required a chest tube for pleural effusion, and one deep wound infection and one pseudarthrosis occurred in the adolescent group. All of these complications required reoperation. Though reoperation rates were greater for adult idiopathic scoliosis (10.7% vs 3.6%) the difference was not statistically significant likely due to the small sample size.

Dr. Lonner asserted that the results add considerably to the information families and surgeons should consider in determining whether the timing for surgery for idiopathic scoliosis should be performed in the adolescent or later in the symptomatic adult.

Morbidity and quality of life in both groups has been outlined in this matched cohort from prospectively collected pediatric and adult spinal deformity registries. Nevertheless, this investigation suffered from some weaknesses. First, the numbers were relatively small. The team had access to several hundred patients with adolescent idiopathic scoliosis who met the inclusion criteria but far fewer adult patients due to the methodology selected.

The group met by committee and excluded the vast majority of adult cases from consideration in cases when any question as to the etiology being idiopathic was raised. This expert consensus was not foolproof but was the best the team could achieve given the nature of the presentation of the adult patient and lack of consistent data in the adult idiopathic scoliosis registry on whether or not the condition was diagnosed during the adolescent years.

As a result of these small numbers, age stratification of the outcomes of interest could not be performed and are of interest for future study with larger cohorts. Dr. Lonner and colleagues would also like to further stratify by curve types to assess relative benefits of intervention early vs late by curve type.

Though an attempt toward that goal was made, the numbers were too small to make definitive conclusions. They also cannot answer the question of the long-term impact of early fusion in adolescent idiopathic scoliosis or whether or not fusionless strategies will change the equation.

Another component of analysis that would be beneficial from a societal perspective centers around the determination of value and cost/benefit of intervening early vs late and associated costs, durability of outcomes, and overall resources required to treat each patient group as well as the impact on employment and role in society.

Cost per quality-adjusted life-year methodology has begun to take hold in the adult spinal deformity literature and is beneficial to determine the cost/benefit to society as impacted by the durability of outcome.

That methodology has not been developed for pediatric patients because children begin largely asymptomatic and are treated prophylactically. Quality of life gains are marginal except for self-image, and it is difficult to model a benefit over time. This methodology should be developed and is an important area of future study.

Conclusions
Dr. Lonner concluded that patients with adolescent idiopathic scoliosis undergo shorter fusions and less estimated blood loss, operative time, length of stay, and major and minor complications than their adult counterparts who have undergone a natural history of curve progression and present for treatment later. Radiographic corrections are similar and quality of life improvements are seen in both groups but to a greater extent in adults who start off with a greater impact of disease on their quality of life. Further study with larger cohorts is required.

Updated on: 02/08/18
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Adolescent Idiopathic Scoliosis Study, Skeletal Maturity and Surgical Considerations
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