A new bioinspired collagen-hydroxyapatite bone graft substitute in adult scoliosis surgery: results at 3-year follow-up

Abstract

Background: Spinal fusion is a common procedure used for surgical treatment of spinal deformity. In recent years, many bone graft substitutes (BGS) have been developed to provide good arthrodesis when the available autologous bone harvested from the patient is not enough. The aim of this study was to analyze the use of a new-generation composite material (RegenOss) made of Mg-hydroxyapatite nanoparticles nucleated on type I collagen to obtain long posterolateral fusion in adult scoliosis surgery.

Methods: A total of 41 patients who underwent spinal fusion for the treatment of adult scoliosis were retrospectively analyzed. According to Lenke classification, visual analog scale (VAS) score and Oswestry Disability Index (ODI) score, radiographic rates of bone union were evaluated before surgery and at 6, 12 and 36 months of follow-up. Fusion was considered to be successful when criteria for Lenke grade A or B were satisfied. Patient-related risk factors were considered for the evaluation of the final outcome.

Results: At 36-month follow-up, radiographic evidence of spinal fusion was present in the majority of patients (95.1%). A time-dependent statistically significant improvement was evidenced after surgery for all clinical outcomes evaluated. Based on the demographic data collected, there were no statistically significant factors determining fusion. The correction of deformity was maintained at different time points. No intraoperative or postoperative complications were recorded.

Conclusions: The present study demonstrated that RegenOss can safely be used to achieve good arthrodesis when associated with autologous bone graft to obtain long spinal fusion in the treatment of adult scoliosis.

Fig. 1

(A) Schematic representation of the biomineralization process used in the synthesis of hydroxyapatite/type I collagen (MGHA/Coll) scaffold. (B) Transmission electron microscopy (TEM) analysis: Collagen fiber completely covered with magnesium-doped hydroxyapatite (MHA) nanoparticles (A) and detail of the disordered crystalline structure of MHA nanoparticles (B).

Fig. 2

The newly developed magnesium-doped hydroxyapatite/type I collagen (MHA/Coll) 3D scaffold developed for bone regeneration.

Fig. 3

Intraoperative photograph showing the malleability and flexibility of the magnesium-doped hydroxyapatite/type I collagen 3D scaffold. The device can be cut and shaped according to the surgeon's needs.

Fig. 4

Intraoperative photograph showing the use of the magnesium-doped hydroxyapatite/type I collagen 3D scaffold in association with local autologous bone graft for posterior fusion in adult scoliosis surgery.

Fig. 5

Patient's X-ray images. (A) The patient underwent T4-ileum fusion, L4 pedicle subtraction osteotomy (PSO) and L3-L4 extreme lateral interbody fusion (XLIF). (B) The patient shows good sagittal balance at 36-month follow-up (sagittal vertical axis [SVA] 0.3 cm).

Fig. 6

Example of posterior and lateral X-ray image at 36 months of follow-up showing successful posterolateral fusion as confirmed by the presence of mature bony trabeculae (arrows), equivalent to Lenke classification grade A, in patient who underwent T10-ileum fusion, L3-L4 anterior column realignment (ACR), L4 pedicle subtraction osteotomy (PSO) and L3-L4+L4-L5 extreme lateral interbody fusion (XLIF) (image kindly provided by the Department of Orthopaedic Surgery, Niguarda Hospital, Milan, Italy).

Fig. 7

Intraoperative photograph of fusion area at 30 months (case of revision surgery in adult scoliosis). Histological analysis performed in a 63-year-old patient who underwent revision surgery, showing newly formed bone and the complete osteointegration of the device at 30 months (image kindly provided by the Department of Orthopaedic Surgery, Niguarda Hospital, Milan, Italy).

Fig. 8

Histological analysis performed in a 63-year-old patient after revision surgery, showing newly formed bone tissue marked by purple-red staining (black arrows) and the complete osteointegration of the device (represented by the white area in the black circle) at 30 months post-op.