1. Results of Growth Friendly Surgery Versus Casting for the Treatment of EOS in Patients with Prader-Willi Syndrome
Jonathan Oore, Braydon Connell, Burt Yaszay, Amer Samdani, Tricia St. Hilaire, Tara Flynn, Ron El-Hawary, Growing Spine and Children’s Spine Study Groups

2. Prader-Willi Syndrome
Prader-Willi syndrome (PWS) is a congenital condition in which genes on the long arm of chromosome 15 are deleted or unexpressed.
Clinically, PWS presents as decreased muscle tone, hypogonadism, stunted growth, mild cognitive impairments, obesity, and insatiable hunger leading to pervasive food-seeking behaviour (hyperphagia).

3. Scoliosis in PWS
Scoliosis is present in 45% to 86% of PWS patients, with severity increasing into adolescence (Greggi et al., 2010).
Two scoliosis types have been identified in PWS patients: “Long-C” curve and idiopathic (Weiss & Goodall, 2009).

4. Purpose / Hypothesis
Purpose: The purpose of this study is to compare the results of casting to growth friendly surgery for children with early onset scoliosis secondary to Prader-Willi syndrome. Hypothesis: Measures of spine deformity will improve for Prader-Willi syndrome patients treated with GFS and with casting; although choice of treatment may affect outcome.

5. Inclusion Criteria Patients consented to GSSG/CSSG database
Diagnosed with Prader-Willi Syndrome at less than 10 years of age
Casting and GFS treatments
Follow-up >2 years from the first visit

6. Methods
PWS patients were identified from two international multi-center EOS databases.
Scoliosis, kyphosis, spine height (T1-S1), right and left hemithoracic heights and widths (R/L HT H/W) were measured pre-treatment, immediately post-op, and at 2 yr f/u.
Severity of complications (SV) were recorded (Smith et al., 2015).

7. Results 23 patients 10 Casted (mean age 1.8yrs)
13 GFS (mean age 5.8yrs)
Two groups were compared:
Pre-treatment
Follow-up (mean f/u 1.9yr casted and 2.2yr GFS)
Measured compared:
Scoliosis
Kyphosis T1-S1 L/R HT H/W Complications (device and disease related)

8. Results
(p-values calculated using 2-tailed, unpaired t-tests)
Complications: Casted patients had 9 complications (4 device related (dev), 5 disease related (dis)) and GFS had 28 complications (23 dev, 5 dis).

9. Results
(p-values calculated using 1-tailed, paired t-tests)

10. Results
(p-values calculated using 2-tailed, unpaired t-tests)
Complications: Complications per patient: higher for GFS 2.2 than Cast 0.9 (p<0.01). Those with BMI>17 had more dev complications (p=0.09) and those GFS >5 yrs age had fewer complications than those ≤5 yrs (p<0.05). There were no SVIII / SVIV complications.

11. Conclusion
At 2 yr f/u, both GFS and casting were effective in treating EOS in PWS patients. GFS had greater improvements in scoliosis, spine height, and RHTH, but a greater complication rate compared to casted patients.

12. References
El-Hawary, R., Chukwunyerenwa, C. Update on Evaluation and Treatment of Scoliosis. Pediatr Clin North Am 61, (2014). El-Hawary, R., Heflin, J., Joukhadar, N., Yasin, M., Skaggs, D. Superior Extension of Upper Instrumented Level in Distraction-Based Surgery: A Surrogate for Clinically Significant PJK. Spine Deformity 2, 505 (2014). Greggi, T., Martikos, K., Lolli, F., Bakaloudis, G., Di Silvestre, M., Cioni, A., Bròdano, G.B., Giacomini, S. Treatment of scoliosis in patients affected with Prader-Willi syndrome using various techniques. Scoliosis 5 (2010). Holm, V.A., Laurnen, E.L. Prader-Willi syndrome and scoliosis. Dev Med Child Neurol 23, (1981). Odent, T., Accadbled, F., Koureas, G., Cournot, M., Moine, A., Diene, G., Molinas, C., Pinto, G., Tauber, M., Gomes, B., Sales de Gauzy, J., Glorion, C. Scoliosis in Patients With Prader-Willi Syndrome. Pediatrics 122 (2008). Smith, J.T., Johnston, C., Skaggs, D., Flynn, J., Vitale, M. A New Classification System to Report Complications in Growing Spine Surgery: A Multicenter Consensus Study. J Pediatr Orthop 35, (2015). Weiss, R., Goodall, D. Scoliosis in patients with Prader Willi Syndrome – comparisons of conservative and surgical treatment. Scoliosis 4 (2009)