Preoperative Disease-Modifying Agents Reduce Postoperative Complications in SMA Scoliosis Surgery

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A recent study presented at MDA 2024 suggests that preoperative use of disease-modifying agents for patients with spinal muscular atrophy leads to less severe postoperative complications following scoliosis surgery.

Jason Howard, MD, pediatric orthopedic surgeon at Nemours/AI duPont Hospital for Children

Jason Howard, MD

Credit: Nemours/AI duPont Hospital for Children

New findings from a study on scoliosis correction show that preoperative use of disease-modifying therapies (DMTs) is associated with less severe postoperative complications among patients with spinal muscular atrophy (SMA).1 These findings suggest DMTs targeting the involved genes of SMA, such as SMN1 and SMN2, could reduce the severity of postoperative outcomes after scoliosis correction.

Among 74 patients (women, 40%) with a total postoperative follow-up duration of 8.0 years (±4.1), 21 had SMA type 1 (28%), 40 had SMA type 2 (54%), 11 had SMA type 3 (15%) and 2 had an unknown SMA type (3%). For scoliosis surgery type, investigators reported that 53 patients (72%) had posterior spinal fusion and 21 (28%) had growing rods, with a mean age of 12.0 years (±2.4) and 6.2 years (±2.9) at surgery, respectively. Notably, in this population, authors noted primary curve was 44º (±20; preop, 74º [±22]; P <.001) and pelvic obliquity correction was 11º (±9; preop, 17º [±11]; P <.001).

Presented at the 2024 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, held March 3-6, in Orlando, Florida, by lead author Jason Howard, MD, a pediatric orthopedic surgeon at Nemours/AI duPont Hospital for Children, postoperative outcomes after scoliosis surgery were evaluated, particularly on the impact of functional level, genetic severity, and use of DMTs. Investigators hypothesized that genetic severity by decreased SMN2 copy number would increase the risk of postoperative complications by Clavien-Dindo (CD) grading (1-2, less severe; 3-5, more severe) and DMT use would be protective for participants.

READ MORE: SRP-9001 Improves Duchenne Muscular Dystrophy Disease Trajectory Despite Failing to Meet Primary End Point in Phase 3 EMBARK Trial

Top Clinical Takeaways

  • Preoperative use of disease-modifying agents is associated with a significant reduction in the severity of post-operative complications in scoliosis surgery for SMA.
  • Despite high post-operative complication rates overall, preoperative DMA treatment resulted in less severe complications, shorter hospital stays, and decreased days intubated postoperatively.
  • The study underscores the potential benefits of preoperative DMA treatment, although pulmonary function did not show significant improvement after scoliosis surgery.

All told, DMT treatment was used preoperatively for 17 patients (23%) and postoperatively for 57 patients (77%), with a mean duration of 2.2 years (±0.8) and 3.8 years (±1.3), respectively. The investigators noted that the SMN2 copy number was available for 31 patients (42%)—13 patients (42%) had less than 3 copies and 18 patients (58%) had at least 3 copies. Investigators also noted that SMA type or SMN2 copy number did not significantly influence postoperative complication rates.

The use of DMT before surgery was reported as associated with similar rates of postoperative complications, but the complications were less severe (DMT, 6%; no DMT, 28%; CD grade, 3-5; P = .05), and patients had a decreased number of days intubated (DMT, 0.2; no DMT, 1.6; P <.0001) and reduced hospital length of stay (DMT, 4.6; no DMT, 11.0 days; P = .0001). In addition, the percentage predicted of forced vital capacity decreased from the preoperative time point to the final follow-up from 60.0% to 51.8% (P = .002), which was deemed unrelated to surgery type (P =.98), DMT use (P = .26), or SMN2 copy number (P =.27).

The authors noted that although postoperative complications were high in frequency overall, they were typically less severe with preoperative DMT treatment (CD grade, 1-2). Additionally, findings showed no improvement in pulmonary function after scoliosis surgery at the final follow-up and were not affected by fusion compared with growth-friendly procedures, DMT treatment, or disease severity. Investigators noted potential benefits of preoperative DMT treatment given the improvements observed in hospital length of stay and days intubated postoperatively.

In a previous systematic review on scoliosis correction among patients with SMA published in Spine Deformity, studies showed that surgery was associated with decreased pulmonary function, suggesting that clinicians should consider the risk–benefit balance when contemplating scoliosis surgery for their patients.2 In this study, investigators reviewed the literature on pulmonary function testing as the primary outcome of pre- and post-scoliosis surgery. Among 14 studies included in the analysis, most showed postoperative pulmonary function progressively declined in patients with SMA. Otherwise, pulmonary function improved in 2 studies, was unchanged in 2 studies, decreased by the rate of decline in 3 studies, and declined initially then returned to baseline in 2 studies. Notably, the authors noted that respiratory and spine-based complications were common among the participants in the selected studies. 

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REFERENCES
1. Howard J, Ciftci S, Shrader W, Scavina M, Heinle R, Mackenzie W. Scoliosis Correction in Spinal Muscular Atrophy: The Influence of Genetic Severity, Function and Disease-Modifying Agents on Post-operative Outcomes. Presented at: 2024 MDA Clinical and Scientific Conference; March 3-6; Poster T442.
2. Alhammoud A, Othman Y, El-Hawary R, Mackenzie WG, Howard JJ. The impact of scoliosis surgery on pulmonary function in spinal muscular atrophy: a systematic review. Spine Deform. 2021;9(4):913-921. doi:10.1007/s43390-021-00302-w
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