19. Long-term experience with anterior cervical discectomy and fusion using a bio-resorbable cage: results from a prospective study

Abstract

<h3>BACKGROUND CONTEXT</h3> Current cervical interbody cage technology is not without limitations. One strategy to overcome its shortcomings led to the development of biodegradable cages. Animal studies and early clinical experience demonstrated gradual resorption of the cage with excellent bony incorporation and high fusion rates. Although much has been written about their advantageous characteristics, most studies followed their patients for short periods. Little has been published on the long-term follow-up of these cages. <h3>PURPOSE</h3> We describe our experience with biodegradable cages made from a resorbable composite material (40% polylactide (PLLA) and 60% beta-tricalcium phosphate (b-TCP)). These were reported to have a high breaking strength but minimal risk of subsidence. They also gradually resorbed, allowing for greater ease in the assessment of bony bridging. <h3>STUDY DESIGN/SETTING</h3> The authors conducted this prospective cohort study with the approval of our local ethics board. This study was conducted at a University Teaching Hospital in Jeddah, Saudi Arabia. <h3>PATIENT SAMPLE</h3> Consecutive patient sample propspectively enrolled. <h3>OUTCOME MEASURES</h3> Radiographic evidence of fusion, cage resorption, cervical alignment measures, failure requiring re-operation. <h3>METHODS</h3> The aim was to describe fusion and complication rates in patients undergoing anterior cervical discectomy and fusion (ACDF) with this novel biodegradable cage. Imaging was acquired and reviewed at preoperative visit, immediately postoperatively and at last follow-up. Systematic literature review: PubMed and EMBASE were searched for experience with these cages in cervical fusion at other centers. <h3>RESULTS</h3> Our center enrolled 27 patients (14 male and 13 female) until termination of this study. Median age was 60 years. Nineteen percent were smokers and 37% were diabetic. In total, 47 cages were implanted. The number of levels operated was: single-level in six cases, two-level in 12 cases, three-level in seven cases and four-level in two cases. Median follow-up was 34 months (IQR = 29.5-38 months). At final follow-up, 85% achieved fusion. Across all levels operated, we encountered a near-uniform loss of disc height and correction. Two patients required revisions due to cage-related complications and two patients developed asymptomatic screw fractures and are being followed. When removing industry-sponsored material, the literature review demonstrated very unfavourable experience with high rates of failure, similar to our series. <h3>CONCLUSIONS</h3> Our long-term experience with resorbable PLLA cages does not support their adoption into clinical practice. Our literature review supports this notion secondary to an unacceptably high complication and revision rate in other clinical settings. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.