Abstract
Purpose: To describe the clinical, biomechanical and radiological features of a spinal implant failure
Method: Over a two year period 45 patients had treatment of spinal stenosis with the X-stop device. 38 had a single level treated, 7 had two level implants. Average age 68. Pre op walking distance 120 meters, Pre op Oswestry Disability Index (ODI) 45%.
11 patients have had implants removed, a 24% implant failure rate. Clinical failure also occurred in two patients unfit for revision. Prospective data on standard spine outcomes were analysed as well as the radiological and biomechanical features of failure.
Results: One year survivorship was 71%. At 6 months the average walking distance improved to 1430 meters, and the average ODI improved to 26%. Some patients exhibit dramatic improvements which obscures the failures.
There were two modes of failure, early, with a failure to improve after the procedure, and late, with an initial improvement and subsequent deterioration.
A consistent feature of late failure is bone resorption around the implant. This is apparent on post operative radiographs and is a progressive. Scalloping and erosion of bone is seen at revision surgery with the implant within a fibrous capsule. Late spinous process fracture occurred in a two level implant as a result of erosion.
Retrieved implants demonstrate scouring of the PEEK surface which increases with time.
Conclusion: Long term surveillance should be mandatory. The implant should be withdrawn from clinical use until trials establish long term efficacy and safety.
Ethics approval: Registered with Hospital new procedures advisory group audit
Interest Statement: No commercial support
Correspondence should be addressed to BASS/BCSS c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
