Silicate-substituted calcium phosphate as a bone graft substitute in surgery for adolescent idiopathic scoliosis

The purpose of this prospective clinical study is to evaluate the clinical and radiographic outcomes using a silicate-substituted calcium phosphate (Si-CaP) as a bone graft substitute in surgery for adolescent idiopathic scoliosis (AIS). In posterior corrective surgery for AIS, harvesting autologous bone from the iliac crest still represents the gold standard to augment the local bone graft though it is comparatively invasive and associated with donor site morbidity. Si-CaP enriched with bone marrow aspirate (BMA) might be an appropriate bone graft extender to overcome these difficulties.

Eighteen female and three male patients with AIS who underwent corrective posterior instrumentation were observed clinically and radiographically for a minimum of 24 months. In all cases, 20-40 ml Si-CaP granules (ACTIFUSE) mixed with BMA from vertebral bodies was used to extend the local bone graft. Fusion was assessed by standardized conventional radiographs regarding loss of correction and implant failure. Clinical outcome was evaluated with use of the Scoliosis Research Society-22 patient Questionnaire (SRS-22) and a Visual Analog Scale (VAS) for back pain.

Cobb angle of major curves averaged 63° preoperatively, 22° after surgery, and 24° at final follow-up, with a maximum loss of correction of 7° recorded after 4 months. No adverse effects related to the study material had been observed. In all patients, there was no evidence of implant failure, and formation of an increasingly densifying 'fusion mass' was visible, as assessed by conventional radiography. VAS score for back pain averaged 1.7 before surgery, 2.3 at discharge, and 1.5 at final follow-up. Outcome assessment using the SRS-22 revealed a significantly enhanced overall health-related quality of life (84 vs. 74 % before surgery; P = 0.0005) due to a significant improvement of the domains 'self image' (77 vs. 59 %; P = 0.0002) and 'pain' (88 vs. 80 %; P = 0.02). Patients' management satisfaction averaged 93 %.

Si-CaP augmented with BMA from vertebral bodies seems to prove an effective, safe, and easy to handle bone graft extender in scoliosis surgery and thus a suitable alternative to bone harvesting procedures.