ANALYSIS OF COMPLICATIONS IN PATIENTS TREATED WITH THE X-STOP INTERSPINOUS PROCESS DECOMPRESSION SYSTEM: PROPOSAL FOR A NOVEL ANATOMIC SCORING SYSTEM FOR PATIENT SELECTION AND REVIEW OF THE LITERATURE

OBJECTIVE: The X-Stop Interspinous Process Decompression System (St. Francis Medical Technologies, Concord, CA) is an interspinous device used with increasing frequency in the treatment of degenerative lumbar spine conditions. To date, limited data are available on complications observed in association with X-Stop procedures, and even less information exists on their underlying causes. The aim of this study was to analyze a series of complications occurring at a single institution and their potential causes and propose an anatomic scoring system that may help to classify patients and prevent complications. METHODS: Sixty-nine patients were treated with the X-Stop. Forty-six single-level and 23 double-level operations (92 devices) were performed according to recommended indications. The mean follow-up duration was 23 months. RESULTS: Eight complications were recorded: 4 device dislocations and 4 spinous process (SP) fractures, including 2 spontaneous fractures of the L4 SP in patients treated at L3-L4 and L4-L5. The following anatomic variants were demonstrated: markedly decreased interspinous distance (kissing spine-like), with concomitant facet joint hypertrophy, a posterior V-shaped interspinous area, limited accessibility of the space between the base and the tip of the SP because of facet joint hypertrophy and variations in the shape of the inferior surface of the cranial SP. CONCLUSION: This is the first study focusing on interspinous distractor complications and the anatomic features of the SP and interspinous areas of the patients, which could potentially be the underlying causes for those complications. The X-Stop can be an effective treatment option, but it is not a panacea for all patients with degenerative lumbar spine conditions. Not only do the clinical indications deserve attention, but also, and most importantly, the patient's anatomic characteristics.