A Prospective Study of the Safety and Efficacy of 3D-printed Non-rigid Biomimetic Implant in Cervical and Thoracolumbar Spine

A Prospective Study of the Safety and Efficacy of 3D-printed Custom-made Non-rigid Biomimetic Implant for Anterior Column Reconstruction in Cervical and Thoracolumbar Spine

Vertebral body resection is a wide accepted procedure in tumor resection, deformity correction, and anterior decompression in spondylosis, ossification of posterior longitudinal ligaments, and spondylodiscitis surgery. However, reconstruction of segmental defect is still challenging to spine surgeon, especially in 3-column resection, such as total en bloc spondylectomy in tumor patients. Various graft or prosthesis for reconstruction has been reported, such as structural allograft, Harms mesh cages, expandable cages, and carbon fiber stackable cages. There are no high evidence level study examining the superiority of those different methods.

Recently, 3D printed vertebral body replacement has been reported in different disease entities as well, such as tumor, Kümmell's disease in osteoporosis, and spondylosis. 3D printed implant comes with superiority in production of complex geometries and regularity of the fine surface detailed that promote bone ingrowth. Although, 3D-printed titanium vertebra could achieved bone integration in human, a systemic review showed that the subsidence noted in 31.4% of spine surgery with 3D printed implants. In spine surgery, the fixation construct is sufficiently stiff, interbody motion can be reduced, and loading sharing promotes bone fusion. On the other hand, if the reconstruction is too stiff, stress shielding at fusion site occurs. The concept of dynamic fusion, as opposed to rigid fusion, has been demonstrated by an anterior cervical interbody fusion study in porcine model, demonstrating good bone formation, less postfusion stiffness, and a trend to less subsidence.

Thus, we developed a 3D printed, custom-made, biomimetic prosthesis, with non-rigid structure, which has been tested in biomechanical study and porcine model, showing good bone formation and less stiffness as well. Therefore, we proposed a prospective clinical study to investigate safety, subsidence, and fusion of this prosthesis.

This is a single-arm prospective observational phase I clinical study to investigate the safety of the non-rigid 3D printed custom-made biomimetic implant. The implants are made of Titanium alloy. Patient receiving 1- to 3-level corpectomy at cervical and thoracolumbar spine. At first stage, we plan to enroll 3 cervical patients, and 3 thoracolumbar patients with non-rigid 3D printed custom-made biomimetic reconstructions. After 3 months observation after the last patients enrolled, we will conduct an interim investigation to investigate those 6 patients. if there is no re-operations due to acute post-operative reconstruction failure. We will continue the study. Total 9 cervical patients, and 9 thoracolumbar patients will be enrolled. Patients are evaluated preoperatively, right after surgery, and 1, 3, 6, 12 months postoperatively. Measure outcomes included overall success, VAS neck and back pain, patient satisfaction, anxiety score, SF-12 MCS/PCS, complications, subsequent surgery rate, and subsidence and fusion rate on radiological examination. Radiological evaluation, including X-ray and computed tomography, will be done pre-operatively, immediately after the surgery, and 1, 3, 6, 12 months postoperatively. In addition, neck disability index (NDI) will be evaluated in cervical patents, and SORGSQ 2.0 self-reported questionnaire will be applied for all oncology patients. The primary endpoint was a FDA composite definition of success comprising clinical improvement and absence of major complications and secondary surgery events.

Inclusion Criteria:

1. Age 20 - 79 years;
2. Patient meet the indication for 1- to 3- level corpectomy, for primary bone tumor at spine, or metastatic tumor at spine.
3. Deficit confirmed by CT, MRI, and X-ray;
4. Pathology level located from C3 to L5.
5. Physically and mentally able and willing to comply with the protocol;
6. Signed informed consent;
7. NTU Spine Multidisciplinary Board confirmed tumor excision surgery is indicated.
8. Life expectancy longer than 6 months (Tokuhashi Scoring System)

Exclusion Criteria:

1. Patient does not meet the indication of corpectomy, which is under the surveillance.
2. More than three vertebrae required corpectomy;
3. Corpectomy levels above C3 and below L5
4. T-score less than -2.5
5. Known allergy to device materials - such as titanium
6. Any diseases or conditions that would preclude accurate clinical evaluation;
7. Daily, high-dose oral and/or inhaled steroid or a history of chronic use of high dose steroids;
8. BMI > 35
9. Life expectancy less than 6 months - (Tokuhashi Scoring System)
10. The subject has received radiation therapy or chemotherapy at the trial site within one year;
11. Anterior spine surgery has been received at or near the spine surgery site;
12. The subject has systemic infection,or focal vertebral infection or trauma;
13. The subject has endocrine disorders or metabolic disorders known to affect bone formation, such as: Paget's disease, renal osteodystrophy, hypothyroidism;
14. The subject has neuromuscular diseases, those at risk of instability, implant fixation failure or postoperative care complications, including: spina bifida, cerebral palsy, and multiple sclerosis;
15. Osteopenia, osteomyelitis;
16. Pregnant women.