Ralph J Mobbs1, Prashanth J Rao2, Kevin Phan2, Philip Hardcastle3, Wen Jie Choy4, Eric R McCartney5, Ross K Druitt6, Christopher A L Mouatt7, Charles C Sorrell8. 1. NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia; Prince of Wales Private Hospital, Sydney, New South Wales, Australia; University of New South Wales Sydney, Sydney, New South Wales, Australia. Electronic address: r.mobbs@unsw.edu.au. 2. NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia; Prince of Wales Private Hospital, Sydney, New South Wales, Australia; University of New South Wales Sydney, Sydney, New South Wales, Australia. 3. Philip Hardcastle Clinic, Perth, Western Australia, Australia. 4. NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia; University of New South Wales Sydney, Sydney, New South Wales, Australia. 5. University of New South Wales Sydney, Sydney, New South Wales, Australia; Deceased. 6. Sialon Ceramics Pty. Ltd., Doyalson North, New South Wales, Australia. 7. Sialon Ceramics Pty. Ltd., Doyalson North, New South Wales, Australia; Currently BC&M Advisory Pty. Ltd., Lindfield, New South Wales, Australia. 8. University of New South Wales Sydney, Sydney, New South Wales, Australia; School of Materials Science and Engineering, University of New South Wales Sydney, Sydney, New South Wales, Australia.
Abstract
BACKGROUND: In this study, a historical case series is reported of reaction bonded silicon nitride (Si3N4) implants for anterior lumbar interbody fusion (ALIF) for a patient population of 30 and surgery levels L3/4, L4/5, and/or L5/S1. Before the study, the only work on Si3N4 as a biomedical material was associated preliminary work, which involved animal trials using a rabbit model. The objective was to undertake the first use of Si3N4 as a biomedical material for humans, as an implant for ALIF. METHODS: The Si3N4 implants were prepared by die-pressing silicon powder and reaction bonding in 95 N2/5 H2 at ∼1400°C for ∼50 hours. The surgeries involved a retroperitoneal approach for L3/4 and L4/5 levels and a transperitoneal approach for L5/S1 level. The patient follow-up involved assessment of radiologic fusion up to 30 years and clinical outcomes to 10 years. RESULTS: The reaction bonded Si3N4 implants were found to be biologically safe and to show high fusion rates with minimal subsidence, no abnormal reaction, and no other complications. The primary outcome measure, visual analog scale back pain, improved from a preoperative mean of 8.4 (range, 6-10) to a mean of 3.7 (range, 0-9) at 5 years and a mean of 4.9 (range, 0-9) at 10 years. The Oswestry Disability Index improved from a preoperative mean of 48 (range, 26-84) to a mean of 35 (range, 4-76) at 10 years. CONCLUSIONS: This study confirms that Si3N4 is biologically safe in the long-term, with capacity for excellent radiologic osseointegration.
BACKGROUND: In this study, a historical case series is reported of reaction bonded silicon nitride (Si3N4) implants for anterior lumbar interbody fusion (ALIF) for a patient population of 30 and surgery levels L3/4, L4/5, and/or L5/S1. Before the study, the only work on Si3N4 as a biomedical material was associated preliminary work, which involved animal trials using a rabbit model. The objective was to undertake the first use of Si3N4 as a biomedical material for humans, as an implant for ALIF. METHODS: The Si3N4 implants were prepared by die-pressing silicon powder and reaction bonding in 95 N2/5 H2 at ∼1400°C for ∼50 hours. The surgeries involved a retroperitoneal approach for L3/4 and L4/5 levels and a transperitoneal approach for L5/S1 level. The patient follow-up involved assessment of radiologic fusion up to 30 years and clinical outcomes to 10 years. RESULTS: The reaction bonded Si3N4 implants were found to be biologically safe and to show high fusion rates with minimal subsidence, no abnormal reaction, and no other complications. The primary outcome measure, visual analog scale back pain, improved from a preoperative mean of 8.4 (range, 6-10) to a mean of 3.7 (range, 0-9) at 5 years and a mean of 4.9 (range, 0-9) at 10 years. The Oswestry Disability Index improved from a preoperative mean of 48 (range, 26-84) to a mean of 35 (range, 4-76) at 10 years. CONCLUSIONS: This study confirms that Si3N4 is biologically safe in the long-term, with capacity for excellent radiologic osseointegration.