At the AAOS 2024 Annual Meeting, Ilkka Helenius, MD, PhD, chief of pediatric orthopaedics and traumatology at Turku University Hospital in Turku, Finland, and colleagues presented a study evaluating long-term pulmonary function outcomes of segmental pedicle screw instrumentation for managing adolescent idiopathic scoliosis (AIS). Despite improvements in lung volume, 38 percent of patients still had impaired lung function at 10-year follow-up. For AAOS Now, Selina C. Poon, MD, MPH, FAAOS, sat down with Dr. Helenius to discuss the key takeaways from his study, including the importance of timely surgical intervention and future studies on this topic.

Dr. Poon: What was the reasoning behind your research question?
Dr. Helenius: Our patients with AIS will hopefully have a long and happy life. We know from previous studies that pulmonary function will be affected by severe thoracic curves. The larger the curve and the smaller the associated thoracic hypokyphosis, the smaller lungs they will have. The aim of our study was actually to evaluate the long-term outcomes of pulmonary function after the current practice, which is segmental pedicle screw instrumentation for AIS. There are no previous studies evaluating the long-term outcome with the current AIS surgical treatment.

In the United States, it is very hard for us to have long-term follow up, because people tend to move around. Do you have the same issues in Finland?
Yes, we do! On the other hand, the Scandinavian countries have very high-quality patient registers, so we can easily identify if our patients are moving, for example, out of our hospital area. So we can track these patients afterward, and we can ask them to get back for these long-term outcome studies. We are very lucky in Finland, because many of the patients and their families are relatively eager to participate in the long-term outcome studies. They feel an additional value of having a long-term evaluation. In Finland, we typically stop the routine follow-up after 2 years postoperatively in these patient groups.

Your study shows that this fusion minimally improves pulmonary function in patients with AIS. Should we still be doing it?
That’s a very good question. I would put it this way: Over the 10-year follow-up period, the first vital capacity, representing the lung volume, improved by a mean of 500 milliliters. When we evaluate these values to normal population, 49 percent of our patients had preoperative impairment in the pulmonary function according to the American Thoracic Society definitions. Then at 10 years’ follow-up, still, 38 percent had lung-volume impairment.

On the other hand, we know from previous studies that as these curves get larger and they continue to progress even after skeletal maturity, the natural history may be a further decline in lung volume. So even if we cannot improve [lung volume] much during the follow-up, it’s still very important to reverse the decline in pulmonary function. This treatment provides the probability for the kind of normal lung-volume development in these adolescents, as we know that the peak lung volume is typically achieved in normal population at the age of 25. It’s very important that we put them back onto this track.

Can we extrapolate these data to the early-onset scoliosis (EOS) population or even the adult deformity population? As you know, it’s very difficult to get these data for these two groups.
Yes. EOS is a very difficult condition. The problem in the EOS patient population is that it is not that easy to evaluate pulmonary function on a 5-year-old patient, but I would anticipate that these patients greatly benefit from the growth-friendly management we are performing. I also assume that in adult spinal deformity, especially in young adults, a similar improvement can be obtained using the strategy we were using in the adolescent population.

Are you planning a follow-up study?
Yes, we are planning to have the 20-year follow-up study in our future protocols. For this study, we got 50 patients out of 64 originally operated [on], so quite a nice amount. Maybe there will be a small reduction in the number of patients, because people then might move abroad or have some more difficulties in coming to these even longer-term follow-up studies.

What is the main takeaway from this study that you would like our members to remember?
AIS is associated with reduced pulmonary function. When these patients fulfill the indication criteria, which is typically more than 45- to 50-degree curves, I think it would be ideal to [treat them] at this phase, because what they lose in pulmonary function can only partially be recovered using surgical treatment. So timely diagnosis and surgical treatment is important in this patient population.

Selina C. Poon, MD, MPH, FAAOS, is a pediatric orthopaedic surgeon and director of research at Shriners Children’s Southern California in Pasadena, California.